query: The most notorious was 252 million years ago; it began when carbon warmed the planet by five degrees, accelerated when that warming triggered the release of methane in the Arctic, and ended with 97 percent of all life on Earth dead.”

positive: Earth Earth ( from Eorðe -LSB- Γαῖα , Gaia -RSB- Terra ) , otherwise known as the World or the Globe , is the third planet from the Sun and the only object in the Universe known to harbor life . It is the densest planet in the Solar System and the largest of the four terrestrial planets .   According to radiometric dating and other sources of evidence , Earth formed about 4.54 billion years ago . Earth 's gravity interacts with other objects in space , especially the Sun and the Moon , Earth 's only natural satellite . During one orbit around the Sun , Earth rotates about its axis over 365 times ; thus , an Earth year is about 365.26 days long . Earth 's axis of rotation is tilted , producing seasonal variations on the planet 's surface . The gravitational interaction between the Earth and Moon causes ocean tides , stabilizes the Earth 's orientation on its axis , and gradually slows its rotation .   Earth 's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years . About 71 % of Earth 's surface is covered with water , mostly by its oceans . The remaining 29 % is land consisting of continents and islands that together have many lakes , rivers and other sources of water that contribute to the hydrosphere . The majority of Earth 's polar regions are covered in ice , including the Antarctic ice sheet and the sea ice of the Arctic ice pack . Earth 's interior remains active with a solid iron inner core , a liquid outer core that generates the Earth 's magnetic field , and a convecting mantle that drives plate tectonics .   Within the first billion years of Earth 's history , life appeared in the oceans and began to affect the Earth 's atmosphere and surface , leading to the proliferation of aerobic and anaerobic organisms . Some geological evidence indicates that life may have arisen as much as 4.1 billion years ago . Since then , the combination of Earth 's distance from the Sun , physical properties , and geological history have allowed life to evolve and thrive . In the history of the Earth , biodiversity has gone through long periods of expansion , occasionally punctuated by mass extinction events . Over 99 % of all species that ever lived on Earth are extinct . Estimates of the number of species on Earth today vary widely ; most species have not been described . Over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival . Humans have developed diverse societies and cultures ; politically , the world has about 200 sovereign states .

positive: Arctic The Arctic ( -LSB- ˈɑrktɪk -RSB- or -LSB- ˈɑrtɪk -RSB- ) is a polar region located at the northernmost part of Earth . The Arctic consists of the Arctic Ocean , adjacent seas , and parts of Alaska ( United States ) , Canada , Finland , Greenland ( Denmark ) , Iceland , Norway , Russia and Sweden . Land within the Arctic region has seasonally varying snow and ice cover , with predominantly treeless permafrost-containing tundra . Arctic seas contain seasonal sea ice in many places .   The Arctic region is a unique area among Earth 's ecosystems . For example , the cultures in the region and the Arctic indigenous peoples have adapted to its cold and extreme conditions . In recent years , Arctic sea ice decline has been caused by global warming . Life in the Arctic includes organisms living in the ice , zooplankton and phytoplankton , fish and marine mammals , birds , land animals , plants and human societies . Arctic land is bordered by the subarctic .

positive: Permafrost In geology , permafrost is ground , including rock or ( cryotic ) soil , at or below the freezing point of water 0 C for two or more years . Most permafrost is located in high latitudes ( in and around the Arctic and Antarctic regions ) , but alpine permafrost may exist at high altitudes in much lower latitudes . Ground ice is not always present , as may be in the case of nonporous bedrock , but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of the ground material . Permafrost accounts for 0.022 % of total water on earth and exists in 24 % of exposed land in the Northern Hemisphere . It also occurs subsea on the continental shelves of the continents surrounding the Arctic Ocean , portions of which were exposed during the last glacial period , with global weather implications .   A global temperature rise of 1.5 C-change above current levels would be enough to start the thawing of permafrost in Siberia , according to one group of scientists .

positive: Eocene The Eocene ( -LSB- pronˈiːəˌsiːn , _ ˈiːoʊ - -RSB- ) Epoch , lasting from , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era . The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch . The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope 13C in the atmosphere was exceptionally low in comparison with the more common isotope 12C . The end is set at a major extinction event called the Grande Coupure ( the `` Great Break '' in continuity ) or the Eocene -- Oligocene extinction event , which may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay . As with other geologic periods , the strata that define the start and end of the epoch are well identified , though their exact dates are slightly uncertain .   The name Eocene comes from the Ancient Greek ἠώς ( ēṓs , `` dawn '' ) and καινός ( kainós , `` new '' ) and refers to the `` dawn '' of modern ( ` new ' ) fauna that appeared during the epoch .

positive: Tundra In physical geography , tundra is a type of biome where the tree growth is hindered by low temperatures and short growing seasons . The term tundra comes through Russian тундра ( tûndra ) from the Kildin Sami word tūndâr `` uplands '' , `` treeless mountain tract '' . There are three types of tundra : Arctic tundra , alpine tundra , and Antarctic tundra . In tundra , the vegetation is composed of dwarf shrubs , sedges and grasses , mosses , and lichens . Scattered trees grow in some tundra regions . The ecotone ( or ecological boundary region ) between the tundra and the forest is known as the tree line or timberline .

negative: Future of Earth The biological and geological future of Earth can be extrapolated based upon the estimated effects of several long-term influences . These include the chemistry at Earth 's surface , the rate of cooling of the planet 's interior , the gravitational interactions with other objects in the Solar System , and a steady increase in the Sun 's luminosity . An uncertain factor in this extrapolation is the ongoing influence of technology introduced by humans , such as climate engineering , which could cause significant changes to the planet . The current Holocene extinction is being caused by technology and the effects may last for up to five million years . In turn , technology may result in the extinction of humanity , leaving the planet to gradually return to a slower evolutionary pace resulting solely from long-term natural processes .   Over time intervals of hundreds of millions of years , random celestial events pose a global risk to the biosphere , which can result in mass extinctions . These include impacts by comets or asteroids with diameters of 5 -- or more , and the possibility of a massive stellar explosion , called a supernova , within a 100-light-year radius of the Sun , called a Near-Earth supernova . Other large-scale geological events are more predictable . If the long-term effects of global warming are disregarded , Milankovitch theory predicts that the planet will continue to undergo glacial periods at least until the Quaternary glaciation comes to an end . These periods are caused by variations in eccentricity , axial tilt , and precession of the Earth 's orbit . As part of the ongoing supercontinent cycle , plate tectonics will probably result in a supercontinent in 250 -- 350 million years . Some time in the next 1.5 -- 4.5 billion years , the axial tilt of the Earth may begin to undergo chaotic variations , with changes in the axial tilt of up to 90 ° .   During the next four billion years , the luminosity of the Sun will steadily increase , resulting in a rise in the solar radiation reaching the Earth . This will result in a higher rate of weathering of silicate minerals , which will cause a decrease in the level of carbon dioxide in the atmosphere . In about 600 million years from now , the level of CO2 will fall below the level needed to sustain C3 carbon fixation photosynthesis used by trees . Some plants use the C4 carbon fixation method , allowing them to persist at concentrations as low as 10 parts per million . However , the long-term trend is for plant life to die off altogether . The extinction of plants will be the demise of almost all animal life , since plants are the base of the food chain on Earth .   In about one billion years , the solar luminosity will be 10 % higher than at present . This will cause the atmosphere to become a `` moist greenhouse '' , resulting in a runaway evaporation of the oceans . As a likely consequence , plate tectonics will come to an end , and with them the entire carbon cycle . Following this event , in about 2 − 3 billion years , the planet 's magnetic dynamo may cease , causing the magnetosphere to decay and leading to an accelerated loss of volatiles from the outer atmosphere . Four billion years from now , the increase in the Earth 's surface temperature will cause a runaway greenhouse effect , heating the surface enough to melt it . By that point , all life on the Earth will be extinct . The most probable fate of the planet is absorption by the Sun in about 7.5 billion years , after the star has entered the red giant phase and expanded to cross the planet 's current orbit .

negative: Paleocene–Eocene Thermal Maximum The Paleocene -- Eocene Thermal Maximum ( PETM ) , alternatively ( ETM1 ) , and formerly known as the `` Initial Eocene '' or '' '' was a time period with more than 8 ° C warmer global average temperature than today . This climate event began at the time boundary between the Paleocene and Eocene geological epochs . The exact age and duration of the event is uncertain but it is estimated to have occurred around 55.5 million years ago .   The associated period of massive carbon injection into the atmosphere has been estimated to have lasted no longer than 20,000 years . The entire warm period lasted for about 200,000 years . Global temperatures increased by 5 -- 8 ° C . The carbon dioxide was likely released in two pulses , the first lasting less than 2,000 years . Such a repeated carbon release is in line with current global warming . A main difference is that during the Paleocene -- Eocene Thermal Maximum , the planet was essentially ice-free .   The onset of the Paleocene -- Eocene Thermal Maximum has been linked to an initial 5 ° C temperature rise and to extreme changes in Earth 's carbon cycle . The period is marked by a prominent negative excursion in carbon stable isotope records from around the globe ; more specifically , there was a large decrease in 13C/12C ratio of marine and terrestrial carbonates and organic carbon .   Stratigraphic sections of rock from this period reveal numerous other changes . Fossil records for many organisms show major turnovers . For example , in the marine realm , a mass extinction of benthic foraminifera , a global expansion of subtropical dinoflagellates , and an appearance of excursion , planktic foraminifera and calcareous nanofossils all occurred during the beginning stages of PETM . On land , modern mammal orders ( including primates ) suddenly appear in Europe and in North America . Sediment deposition changed significantly at many outcrops and in many drill cores spanning this time interval .   At least since 1997 , the Paleocene -- Eocene Thermal Maximum has become a focal point of considerable geoscience research because it probably provides the best past analog by which to understand impacts of global climate warming and of massive carbon input to the ocean and atmosphere , including ocean acidification . Although it is now widely accepted that the PETM represents a `` case study '' for global warming and massive carbon input to Earth 's surface , the cause , details and overall significance of the event remain perplexing .

negative: History of Earth The history of Earth concerns the development of the planet Earth from its formation to the present day . Nearly all branches of natural science have contributed to the understanding of the main events of the Earth 's past . The age of Earth is approximately one-third of the age of the universe . An immense amount of geological change has occurred in that timespan , accompanied by the emergence of life and its subsequent evolution .   Earth formed around 4.54 billion years ago by accretion from the solar nebula . Volcanic outgassing probably created the primordial atmosphere and then the ocean ; but the atmosphere contained almost no oxygen and so would have been toxic to most modern life including humans . Much of the Earth was molten because of frequent collisions with other bodies which led to extreme volcanism . A giant impact collision with a planet-sized body named Theia while Earth was in its earliest stage , also known as Early Earth , is thought to have been responsible for forming the Moon . Over time , the Earth cooled , causing the formation of a solid crust , and allowing liquid water to exist on the surface .   The geological time scale ( GTS ) clock ( see graphic ) depicts the larger spans of time from the beginning of the Earth as well as a chronology of some definitive events of Earth history . The Hadean Eon represents time before the reliable ( fossil ) record of life beginning on Earth ; it began with the formation of the planet and ended at 4.0 billion years ago as defined by international convention . The Archean and Proterozoic eons follow ; they produced the abiogenesis of life on Earth and then the evolution of early life . The succeeding eon is the Phanerozoic , which is represented by its three component eras : the Palaeozoic ; the Mesozoic , which spanned the rise , reign , and climactic extinction of the huge dinosaurs ; and the Cenozoic , which presented the subsequent development of dominant mammals on Earth .   Hominins , the earliest direct ancestors of the human clade , rose sometime during the latter part of the Miocene epoch ; the precise time marking the first hominins is broadly debated over a current range of 13 to 4 mya . The succeeding Quaternary period is the time of recognizable humans , i.e. , the genus Homo , but that period 's two million-year-plus term of the recent times is too small to be visible at the scale of the GTS graphic . ( Notes re the graphic : Ga means `` billion years '' ; Ma , `` million years '' . )   The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago , during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon . There are microbial mat fossils such as stromatolites found in 3.48 billion-year-old sandstone discovered in Western Australia . Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old metasedimentary rocks discovered in southwestern Greenland as well as `` remains of biotic life '' found in 4.1 billion-year-old rocks in Western Australia . According to one of the researchers , `` If life arose relatively quickly on Earth ... then it could be common in the universe . ''   Living forms derived from photosynthesis appeared between 3.2 and 2.4 billion years ago and began enriching the atmosphere with oxygen . Life remained mostly small and microscopic until about 580 million years ago , when complex multicellular life arose , developed over time , and culminated in the Cambrian Explosion about 541 million years ago . This event drove a rapid diversification of life forms on Earth that produced most of the major phyla known today ; and it marked the end of the Proterozoic Eon and the beginning of the Cambrian Period of the Paleozoic Era . More than 99 percent of all species , amounting to over five billion species , that ever lived on Earth are estimated to be extinct . Estimates on the number of Earth 's current species range from 10 million to 14 million , of which about 1.2 million have been documented and over 86 percent have not yet been described . More recently , in May 2016 , scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described .   Geological change has been a constant of Earth 's crust since the time of its formation , and biological change since the first appearance of life . Species continue to evolve , taking on new forms , splitting into daughter species or going extinct in the process of adapting or dying in response to ever-changing physical environments . The process of plate tectonics continues to play a dominant role in the shaping of Earth 's oceans and continents and the living species they harbor . Changes in the biosphere -- now dominated by human activity -- continue , in turn , to produce significant effects on the atmosphere and other systems of the Earth 's surface , such as the integrity of the ozone layer , the proliferation of greenhouse gases , the conditions of productive soils and clean air and water , and others .

negative: Biodiversity Biodiversity a portmanteau of `` biological diversity , '' generally refers to the variety and variability of life on Earth . According to the United Nations Environment Programme , biodiversity typically measures variation at the genetic , the species , and the ecosystem level . Terrestrial biodiversity tends to be greater near the equator , which seems to be the result of the warm climate and high primary productivity . Biodiversity is not distributed evenly on Earth , and is richest in the tropics . These tropical forest ecosystems cover less than 10 per cent of earth 's surface , and contain about 90 percent of the world 's species . Marine biodiversity tends to be highest along coasts in the Western Pacific , where sea surface temperature is highest and in the mid-latitudinal band in all oceans . There are latitudinal gradients in species diversity . Biodiversity generally tends to cluster in hotspots , and has been increasing through time , but will be likely to slow in the future .   Rapid environmental changes typically cause mass extinctions . More than 99.9 percent of all species , amounting to over five billion species , that ever lived on Earth are estimated to be extinct . Estimates on the number of Earth 's current species range from 10 million to 14 million , of which about 1.2 million have been documented and over 86 percent have not yet been described . More recently , in May 2016 , scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described . The total amount of related DNA base pairs on Earth is estimated at 5.0 x 1037 and weighs 50 billion tonnes . In comparison , the total mass of the biosphere has been estimated to be as much as 4 TtC ( trillion tons of carbon ) . In July 2016 , scientists reported identifying a set of 355 genes from the Last Universal Common Ancestor ( LUCA ) of all organisms living on Earth .   The age of the Earth is about 4.54 billion years old . The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago , during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon . There are microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia . Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old meta-sedimentary rocks discovered in Western Greenland . More recently , in 2015 , `` remains of biotic life '' were found in 4.1 billion-year-old rocks in Western Australia . According to one of the researchers , `` If life arose relatively quickly on Earth . . then it could be common in the universe . ''   Since life began on Earth , five major mass extinctions and several minor events have led to large and sudden drops in biodiversity . The Phanerozoic eon ( the last 540 million years ) marked a rapid growth in biodiversity via the Cambrian explosion -- a period during which the majority of multicellular phyla first appeared . The next 400 million years included repeated , massive biodiversity losses classified as mass extinction events . In the Carboniferous , rainforest collapse led to a great loss of plant and animal life . The Permian -- Triassic extinction event , 251 million years ago , was the worst ; vertebrate recovery took 30 million years . The most recent , the Cretaceous -- Paleogene extinction event , occurred 65 million years ago and has often attracted more attention than others because it resulted in the extinction of the dinosaurs .   The period since the emergence of humans has displayed an ongoing biodiversity reduction and an accompanying loss of genetic diversity . Named the Holocene extinction , the reduction is caused primarily by human impacts , particularly habitat destruction . Conversely , biodiversity impacts human health in a number of ways , both positively and negatively .   The United Nations designated 2011 -- 2020 as the United Nations Decade on Biodiversity .

negative: Life Entity The Life Entity is a fictional creature , a physical embodiment of all life within the DC Universe . Long ago starting all life from the planet Earth , it went on to create the seven entities of the Emotional Electromagnetic Spectrum , and was hidden in a dimensional tear within the Earth by the Guardians of the Universe when they discovered its existence in order to preserve it from exploitation and possible harm .

negative: Occluded front An occluded front is formed during the process of cyclogenesis when a cold front overtakes a warm front . When this occurs , the warm air is separated ( occluded ) from the cyclone center at the Earth 's surface . The point where the warm front and the occluded front meet ( and consequently the nearest location of warm air to the center of the cyclone ) is called the triple point .   The trowal ( short for TROugh of Warm air ALoft ) is the projection on the Earth 's surface of the trough of warm air aloft formed during the occlusion process of the depression .

negative: Evolution of insects Based on genome sequencing data , it is estimated that the class of insects originated on Earth about 480 million years ago , in the Ordovician , at about the same time terrestrial plants appeared . Insects evolved from a group of crustaceans . The first insects were land bound , but about 400 million years ago in the Devonian period one lineage of insects evolved flight , the first animals to do so . The oldest definitive insect fossil , Rhyniognatha hirsti , is estimated to be . Global climate conditions changed several times during the history of Earth , and along with it the diversity of insects . The Pterygotes ( winged insects ) underwent a major radiation in the Carboniferous ( 356 to 299 million years ago ) while the Endopterygota ( insects that go through different life stages with metamorphosis ) underwent another major radiation in the Permian ( 299 to 252 million years ago ) .   Most extant orders of insects developed during the Permian period . Many of the early groups became extinct during the mass extinction at the Permo-Triassic boundary , the largest extinction event in the history of the Earth , around . The survivors of this event evolved in the Triassic ( 252 to 201 million years ago ) to what are essentially the modern insect orders that persist to this day . Most modern insect families appeared in the Jurassic ( 201 to 145 million years ago ) .   In an important example of co-evolution , a number of highly successful insect groups -- especially the Hymenoptera ( wasps , bees and ants ) and Lepidoptera ( butterflies ) as well as many types of Diptera ( flies ) and Coleoptera ( beetles ) -- evolved in conjunction with flowering plants during the Cretaceous ( 145 to 66 million years ago ) .   Many modern insect genera developed during the Cenozoic that began about 66 million years ago ; insects from this period onwards frequently became preserved in amber , often in perfect condition . Such specimens are easily compared with modern species , and most of them are members of extant genera .

negative: Wetland methane emissions As one of the most significant natural sources of atmospheric methane , wetlands remain a major area of concern with respect to climate change . Wetlands are characterized by water-logged soils and distinctive communities of plant and animal species that have evolved and adapted to the constant presence of water . Due to this high level of water saturation as well as warm weather , wetlands are one of the most significant natural sources of atmospheric methane .   Most methanogenesis , or methane production , occurs in oxygen-poor environments . Because the microbes that live in warm , moist environments consume oxygen more rapidly than it can diffuse in from the atmosphere , wetlands are the ideal anaerobic , or oxygen poor , environments for fermentation .   Fermentation is a process used by certain kinds of microorganisms to break down essential nutrients . In a process called acetoclastic methanogenesis , microorganisms from the classification domain archaea produce methane by fermenting acetate and H2-CO2 into methane and carbon dioxide .   H3C-COOH → CH4 + CO2   Depending on the wetland and type of archaea , hydrogenotrophic methanogenesis , another process that yields methane , can also occur . This process occurs as a result of archaea oxidizing hydrogen with carbon dioxide to yield methane and water .   4H2 + CO2 → CH4 + 2H2O

negative: Evolutionary history of life The evolutionary history of life on Earth traces the processes by which living and fossil organisms have evolved since life appeared on the planet , until the present day . Earth formed about 4.5 billion years ( Ga ) ago and there is evidence that life appeared as early as 4.1 Ga. . The similarities between all present-day organisms indicate the presence of a common ancestor from which all known species have diverged through the process of evolution . More than 99 percent of all species , amounting to over five billion species , that ever lived on Earth are estimated to be extinct . Estimates on the number of Earth 's current species range from 10 million to 14 million , of which about 1.9 million are estimated to have been named and 1.6 million documented in a central database to date . More recently , in May 2016 , scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described .   The earliest evidence for life on Earth is graphite found to be a biogenic substance in 3.7 billion-year-old metasedimentary rocks discovered in western Greenland and microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia . More recently , in 2015 , `` remains of biotic life '' were found in 4.1 billion-year-old rocks in Western Australia . In March 2017 , researchers reported evidence of possibly the oldest forms of life on Earth . Putative fossilized microorganisms were discovered in hydrothermal vent precipitates in the Nuvvuagittuq Belt of Quebec , Canada , that may have lived as early as 4.280 billion years ago , not long after the oceans formed 4.4 billion years ago , and not long after the formation of the Earth 4.54 billion years ago . According to biologist Stephen Blair Hedges , `` If life arose relatively quickly on Earth ... then it could be common in the universe . ''   Microbial mats of coexisting bacteria and archaea were the dominant form of life in the early Archean and many of the major steps in early evolution are thought to have taken place within them . The evolution of photosynthesis , around 3.5 Ga , eventually led to a buildup of its waste product , oxygen , in the atmosphere , leading to the great oxygenation event , beginning around 2.4 Ga. . The earliest evidence of eukaryotes ( complex cells with organelles ) dates from 1.85 Ga , and while they may have been present earlier , their diversification accelerated when they started using oxygen in their metabolism . Later , around 1.7 Ga , multicellular organisms began to appear , with differentiated cells performing specialised functions . Sexual reproduction , which involves the fusion of male and female reproductive cells ( gametes ) to create a zygote in a process called fertilization is , in contrast to asexual reproduction , the primary method of reproduction for the vast majority of macroscopic organisms , including almost all eukaryotes ( which includes animals and plants ) . However the origin and evolution of sexual reproduction remain a puzzle for biologists though it did evolve from a common ancestor that was a single celled eukaryotic species . Bilateria , animals with a front and a back , appeared by 555 Ma ( million years ago ) .   The earliest land plants date back to around 450 Ma , although evidence suggests that microorganisms formed the earliest terrestrial ecosystems , at least 2.9 Ga. . Microorganisms are thought to have paved the way for the inception of land plants in the Phanerozoic . Land plants were so successful that they are thought to have contributed to the Late Devonian extinction event . Ediacara biota appear during the Ediacaran period , while vertebrates , along with most other modern phyla originated about during the Cambrian explosion . During the Permian period , synapsids , including the ancestors of mammals , dominated the land , but most of this group became extinct in the Permian -- Triassic extinction event . During the recovery from this catastrophe , archosaurs became the most abundant land vertebrates ; one archosaur group , the dinosaurs , dominated the Jurassic and Cretaceous periods . After the Cretaceous -- Paleogene extinction event killed off the non-avian dinosaurs , mammals increased rapidly in size and diversity . Such mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify .

negative: Emission Reduction Unit The emission reduction unit ( ERU ) is an emissions unit issued under a Joint Implementation project in terms of the Kyoto Protocol . An ERU represents a reduction of greenhouse gases under the Joint Implementation mechanism , where it represents one tonne of equivalent reduced .   To allow comparison between the different effects of gases on the environment , scientists have defined multipliers for gases that compare their greenhouse potency ( global warming potential ) relative to that of carbon dioxide .   One example of a Joint Implementation project resulting in an emission reduction unit , is the production of biogases by landfill sites . These gases consist of mainly methane which escapes to the atmosphere if it is not collected . The main reason for dealing with methane is that it has a 100-year global warming potential multiplier of 25 compared to carbon dioxide ( i.e. has 25 times the greenhouse potency ) . Collection of methane is usually accompanied by its combustion . Burning one tonne of methane produces nearly 3 tonnes of , thus reducing its greenhouse effect by ( 25-3 = 22 ) ERU .   In December 2012 , ERU prices crashed to a low of 15 euro cents before recovering to 23c after news that EU 's Climate Change Committee was to vote on a ban of ERUs from countries that have not signed up to a second commitment period under the Kyoto Protocol .   In January 2013 , Bloomberg reported that emission reduction unit prices declined 89 percent in 2012

negative: Warmness on the Soul `` Warmness on the Soul '' is the first EP/single by Avenged Sevenfold . It was released on August 8 , 2001 by Good Life Recordings . The release features the video for the title track , `` Warmness on the Soul '' as an Enhanced CD bonus . The EP was the first release to feature guitarist , Synyster Gates . All of the songs are included on Avenged Sevenfold 's debut album , Sounding the Seventh Trumpet , except for the heavy metal version of `` To End the Rapture '' , which was later featured on the album 's re-release by Hopeless Records .

negative: Mobilehydricity Mobilehydricity is the process of using hydrogen gas as an energy carrier to power any type of electrical or mechanical device . An energy carrier is a substance or system that moves energy in a usable form from one place to another . Electricity is the most well-known energy carrier . We use electricity to move the energy in coal , uranium , and other energy sources from power plants to homes and businesses . We also use electricity to move the energy in gasoline to power our vehicles . The down side is that coal , uranium and gasoline are all resources which are in limited supply and when burned emit toxic pollution to our environment . Using hydrogen as a supplement energy carrier makes sense because it is plentiful and its only waste byproduct is water .   Since hydrogen does n't exist on earth naturally as a gas , we must extract it from other elements . We can separate hydrogen atoms from water , biomass , or natural gas molecules . The two most common methods for producing hydrogen are steam reforming and water electrolysis  ( water splitting ) .   Steam reforming is currently the least expensive method of producing hydrogen and accounts for about 95 percent of the hydrogen produced in the United States . It is used in industries to separate hydrogen atoms from carbon atoms in methane ( CH4 ) . Because methane  is a fossil fuel , the process of steam reforming results in greenhouse gas emissions that are linked with global warming .   Water electrolysis is a process that splits hydrogen from water . It results in no emissions but it is currently a very expensive process . New technologies are being developed all the time . Just a few years ago it became economically feasible to generate hydrogen from self-contained modules called disseminators . These units are now small enough to be attached to portable generators , outdoor cooking grills , and even cars .   Category : Hydroelectricity

negative: Crimes of the Hot `` Crimes of the Hot '' is the eighth episode in the fourth production season of the American animated television series Futurama . It originally aired on the Fox network in the United States on November 10 , 2002 . The episode was written by Aaron Ehasz and directed by Peter Avanzino . Al Gore guest stars as his own preserved head in a jar , his second appearance in the series . The episode tackles the topic of global warming as the Planet Express crew is sent to retrieve Earth 's yearly ice supply in order to keep the planet cool . When they are unable to retrieve the ice , the Earth is forced to search for other ways to solve their global warming problem . In 2003 , the episode was nominated for an Environmental Media Award .

negative: Enhanced coal bed methane recovery Enhanced coal bed methane recovery is a method of producing additional coalbed methane from a source rock , similar to enhanced oil recovery applied to oil fields . Carbon dioxide ( CO2 ) injected into a bituminous coal bed would occupy pore space and also adsorb onto the carbon in the coal at approximately twice  the rate of methane ( CH4 ) , allowing for potential enhanced gas recovery . This technique may be used in conjunction with carbon capture and storage in mitigation of global warming where the carbon dioxide that is sequestered is captured from the output of fossil fuel power plants .   A research project at ETH Zurich is studying the process of pumping carbon dioxide into unminable coal seams and recovering the methane that is subsequently displaced .   An extensive experimental investigation about the process of desorbing methane by adsorbing carbon dioxide in real coal samples was performed . The proof of principle and the technical feasibility of the method could be verified with these measurements . These research results indicate that CBM can become an alternative to conventional natural gas . ECBM provides additional to CBM the advantage of long-term CO2 storage in the underground coal seams .   However , without other incentives , enhanced coal bed methane recovery is not economical as the commercial value of the released methane does not completely offset the cost of pumping .   Penetration of CO2 into coal is simulated using a stress-enhanced diffusion model .

negative: Outline of life forms A life form or lifeform is an entity or being that is living .   Estimates on the number of Earth 's current species range from 10 million to 14 million , of which about 1.2 million have been documented and over 86 percent have not yet been described . More recently , in May 2016 , scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described .   More than 99 % of all species , amounting to over five billion species , that ever lived on Earth are estimated to be extinct .

negative: Mark Z. Jacobson Mark Zachary Jacobson ( born 1965 ) is professor of civil and environmental engineering at Stanford University and director of its Atmosphere and Energy Program . Jacobson develops computer models about the effects of different energy technologies and their emissions on air pollution and climate . He has done influential research on the role of aerosols and black carbon on the climate and is regarded as a leading aerosol climate modeler .   According to Jacobson , a speedy transition to clean , renewable energy is required to reduce the potential acceleration of global warming , including the disappearance of the Arctic Sea ice . This change will also eliminate 2.5 -- 3 million deaths worldwide each year , related to air pollution , and reduce disruption associated with fossil fuel shortages .

negative: HD 113766 HD 113766 is a binary star system located 424 light years from Earth in the direction of the constellation Centaurus . The star system is approximately 10 million years old and both stars are slightly more massive than our sun . The two are separated by an angle of 1.3 arcseconds , which , at the distance of this system , corresponds to a projected separation of at least 170 AU .   What makes HD 113766 special is the presence of a large belt of warm ( ~ 440 K ) dust surrounding the star HD 113766 A . The dense dust belt , more than 100 times more massive than our own asteroid belt , is thought to be collapsing to form a rocky planet , which when it has formed will lie within the star 's terrestrial habitable zone where liquid water can exist on its surface . HD 113766 represents the most well understood system in a growing class of objects that should provide more clues to how rocky planets like the Earth formed .

negative: Carbon-based fuel Carbon-based fuel is any fuel principally from the oxidation or burning of carbon . Carbon-based fuels are of two main kinds , biofuels and fossil fuels . Whereas biofuels are derived from recent-growth organic matter and are typically harvested , as with logging of forests and cutting of corn , fossil fuels are of prehistoric origin and are extracted from the ground , the principal fossil fuels being oil , coal , and natural gas .   From an economic policy perspective , an important distinction between biofuels and fossil fuels is that only the former is sustainable or renewable .   Whereas we can continue to obtain energy from biofuels indefinitely in principle , the Earth 's reserves of fossil fuels was determined millions of years ago and is therefore fixed as far as our foreseeable future is concerned . The great variability in the ease of extraction of fossil fuels however makes its endgame scenario one of increasing prices over one or more centuries rather than of abrupt exhaustion .   From the perspective of climate and ecology , biofuels and fossil fuels have in common that they contribute to the production of atmospheric carbon dioxide , which has emerged in recent decades as the fastest-changing greenhouse gas , whose principal impacts are global warming and ocean acidification . However biofuels actively participate in the carbon cycle today by photosynthesizing carbon dioxide , unlike fossil fuels whose participation was long ago , and can therefore in principle bring atmospheric CO2 into an equilibrium not possible with the continued use of fossil fuel . But in practice photosynthesis is a slow process , and the additional fuel produced by artificial methods of accelerating it such as application of fertilizer tends to be offset by the energy consumed by the accelerating processes , to a degree currently under active debate . In contrast the speed of photosynthesis is immaterial for fossil fuels because they had millions of years in which to accumulate . Burning of both fossil fuels and biofuels usually also produces carbon monoxide , which is toxic and can kill a person after mixing with the haemoglobin of the blood , increasing its concentration in the body . Biofuels and fossil fuels may also produce many other air pollutants depending on the contents of the fuel .

negative: Warm Your Heart Warm Your Heart is a 1991 album released by American R&B / soul singer Aaron Neville , ( his second album ) . The album features the singles `` Everybody Plays the Fool '' , `` Somewhere , Somebody '' and `` Close Your Eyes '' . The `` Close Your Eyes '' single also featured album producer Linda Ronstadt on guest vocals . The pair had previously collaborated on the songs `` Do n't Know Much '' , `` All My Life '' and `` When Something Is Wrong with My Baby '' .

negative: West Spitsbergen Current The West Spitsbergen Current ( WSC ) is a warm , salty current that runs poleward just west of Spitsbergen , ( formerly called West Spitsbergen ) , in the Arctic Ocean . The WSC branches off the Norwegian Atlantic Current in the Norwegian Sea . The WSC is of importance because it drives warm and salty Atlantic Water into the interior Arctic . The warm and salty WSC flows north through the eastern side of Fram Strait , while the East Greenland Current ( EGC ) flows south through the western side of Fram Strait . The EGC is characterized by being very cold and low in salinity , but above all else it is a major exporter of Arctic sea ice . Thus , the EGC combined with the warm WSC makes the Fram Strait the northernmost ocean area having ice-free conditions throughout the year in all of the global ocean .

negative: Effects of global warming on oceans Global warming can affect sea levels , coastlines , ocean acidification , ocean currents , seawater , sea surface temperatures , tides , the sea floor , weather , and trigger several changes in ocean bio-geochemistry ; all of these affect the functioning of a society .

negative: Uunartoq Qeqertaq Uunartoq Qeqertaq , Greenlandic for `` The Warming Island '' , is an island off the east central coast of Greenland , 550 km north of the Arctic Circle . It became recognised as an island only in September 2005 , by US explorer Dennis Schmitt . It was attached to the mainland of Liverpool Land by glacial ice even in 2002 , when the ice shelves began retreating rapidly in this area , so that by 2005 it was no longer attached to the mainland . Members of the scientific community believe this newly discovered island is a direct result of global warming . The island has three large peninsulas , and thus resembles the letter W , or the Chinese character 山 .

negative: Chaotian (geology) -RCB- -RCB- em ''  | align = `` center '' colspan = 2 style = `` background-color : '' | Chaotian Eon/Era5000 -- 4600 million years ago 4600 -- 4404 million years ago  | -  | align = `` center '' colspan = 2 |  | -  | -RCB-   In the geologic record the Chaotian eon or era is unofficially proposed to denote the time preceding the solidification of the Earth 's crust and the formation of Earth 's moon , it is the earliest era within the eon of Hadean . It lasted 196 million years , at to the beginning of the Zirconian era , . It is named after Chaos , the primeval void in Greek mythology . The Chaotian sets in with the emergence of Earth at 4.6 billion years ago . Its upper limit and thus the transition to the Zirconian era is defined by the occurrence of the first conservation capable mineral . These are zirconium , the oldest mineral in the Jack Hills of Narryer Gneiss Terrane in Western Australia ( Yilgarn craton ) found and were dated 4,404 ± 8 million years ago   According to first proposal , it precedes the Hadean eon and is the earliest eon in Earth 's history as a planet . The end of the Chaotian was marked by the hypothetical collision of the proto-Earth and a planet-sized body named Theia , leading to the formation of the Moon .   Alternatively it is defined as the first era of the Hadean eon , before the formation of the first crust on the Earth . As of 2012 , it is considered to be part of a proposed revision of the Precambrian time scale .

negative: Politics of global warming The complex politics of global warming results from numerous cofactors arising from the global economy 's interdependence on carbon dioxide emitting hydrocarbon energy sources and because carbon dioxide is directly implicated in global warming -- making global warming a non-traditional environmental challenge .

negative: Warm Springs Historic District Warm Springs Historic District is a historic district in Warm Springs , Georgia . It includes Franklin Delano Roosevelt 's Little White House and the Roosevelt Warm Springs Institute for Rehabilitation , where Roosevelt indulged in its warm springs . Other buildings in the district tend to range from the 1920s and 1930s . Much of the district looks the same as it did when Roosevelt frequented the area .   Evidence indicates that prehistoric man was the first to use the springs , and as when Roosevelt used the springs , the temperature was 89 ° F.

negative: Eocene Thermal Maximum 2 Eocene Thermal Maximum 2 ( ETM-2 ) , also called H-1 or the Elmo ( Eocene Layer of Mysterious Origin ) event , was a transient period of global warming that occurred approximately 53.7 million years ago ( Ma ) . It appears to be the second major hyperthermal that punctuated the long-term warming trend from the Late Paleocene through the early Eocene ( 58 to 50 Ma ) .   The hyperthermals were geologically brief time intervals ( < 200,000 years ) of global warming and massive carbon input . The most extreme and best-studied event , the Paleocene-Eocene Thermal Maximum ( PETM or ETM-1 ) , occurred about 1.8 million years before ETM-2 , at approximately 55.5 Ma . Other hyperthermals likely followed ETM-2 at nominally 53.6 Ma ( H-2 ) , 53.3 ( I-1 ) , 53.2 ( I-2 ) and 52.8 Ma ( informally called K , X or ETM-3 ) . The number , nomenclature , absolute ages and relative global impact of the Eocene hyperthermals are the source of much current research .  In any case , the hyperthermals appear to have ushered in the Early Eocene Climatic Optimum , the warmest interval of the Cenozoic Era . They also definitely precede the Azolla event at about 49 Ma .   ETM-2 is clearly recognized in sediment sequences by analyzing the stable carbon isotope composition of carbon-bearing material . The 13C/12C ratio of calcium carbonate or organic matter drops significantly across the event . This is similar to what happens when one examines sediment across the PETM , although the magnitude of the negative carbon isotope excursion is not as large . The timing of Earth system perturbations during ETM-2 and the PETM also appear different . Specifically , the onset of ETM-2 may have been longer ( perhaps 30,000 years ) while the recovery seems to have been shorter ( perhaps < 50,000 years ) . ( Note , however , that the timing of short-term carbon cycle perturbations during both events remains difficult to constrain ) .   A thin clay-rich horizon marks ETM-2 in marine sediment from widely separated locations . In sections recovered from the deep-sea ( for example those recovered by Ocean Drilling Program Leg 208 on Walvis Ridge ) , this layer is caused by dissolution of calcium carbonate . However , in sections deposited along continental margins ( for example those now exposed along the Clarence River , New Zealand ) , the clay-rich horizon represents dilution by excess accumulation of terrestrial material entering into the ocean . Similar changes in sediment accumulation are found across the PETM . In sediment from Lomonosov Ridge in the Arctic Ocean , intervals across both ETM-2 and the PETM shows signs of higher temperature , lower salinity and lower dissolved oxygen .   The PETM and ETM-2 are thought to have a similar generic origin , although this idea is at the edge of current research . During both events , a tremendous amount of 13C-depleted carbon rapidly entered the ocean and atmosphere . This decreased the 13C/12C ratio of carbon-bearing sedimentary components , and dissolved carbonate in the deep ocean . Somehow the carbon input was coupled to an increase in Earth surface temperature and a greater seasonality in precipitation , which explains the excess terrestrial sediment discharge along continental margins . Possible explanations for changes during ETM-2 are the same as those for the PETM , and are discussed under the latter entry .   The H-2 event appears to be a `` minor '' hyperthermal that follows ETM-2 ( H-1 ) by about 100,000 years . This has led to speculation that the two events are somehow coupled and paced by changes in orbital eccentricity .   As in the case of the PETM , reversible dwarfing of mammals has been noted during the ETM-2 .

negative: The Lost Worlds of Planet Earth `` The Lost Worlds of Planet Earth '' is the ninth episode of the American documentary television series Cosmos : A Spacetime Odyssey . It premiered on May 4 , 2014 on Fox , and aired on May 5 , 2014 on National Geographic Channel . The episode was directed by Brannon Braga , written by Ann Druyan and Steven Soter , and featured the voice of Amanda Seyfried as Geologist Marie Tharp . The episode explores the history of the Earth starting with the period of the Late Heavy Bombardment , approximately `` 3.8 to 4.1 Billion years ago during which the Moon , Mercury , Venus , Earth and were battered by space debris . '' Host Neil deGrasse Tyson then delves into the biography of the Earth , expressed `` in its continents , oceans and life living on and in them , saying ` the past is another planet , ' '' alluding to how plate tectonics have shaped the Earth over millions of years .   The episode received a 1.6 / 5 in the 18-49 rating/share , with 4.08 million American viewers watching on Fox .

negative: Abiogenesis Abiogenesis ( British English : -LSB- ˌeɪˌbaɪoʊˈdʒɛnᵻsᵻs , _ - ˌbaɪə - -RSB- , -LSB- - en - ˌbiːoʊ - , _ - ˌbiːə - -RSB- ) , biopoiesis , \ \ or informally , the origin of life , is the natural process by which life arises from non-living matter , such as simple organic compounds . Abiogenesis is studied through a combination of paleontology , laboratory experiments and extrapolation from the characteristics of modern organisms , and aims to determine how pre-life chemical reactions gave rise to life on Earth .   The study of abiogenesis can be geophysical , chemical , or biological , with more recent approaches attempting a synthesis of all three . Life itself is dependent upon the specialized chemistry of carbon and water and is largely based upon five different families of chemicals . Lipids are fatty molecules comprising large chemical chains of hydrocarbons and play an important role in the structure of living cell membranes , actively and passively determining the transport of other molecules into and out of cells . Carbohydrates are sugars , and as monomer units can be assembled into polymers called polysaccharides , such as cellulose , the rigid chemical of most plant cell walls . Nitrogenous bases are organic molecules in which the amine group of nitrogen , combined with two hydrogen atoms , plays an important part . Chlorophyll is based upon a porphyrin ring derived from amine monomer units , and is important in the capture of the energy needed for life . Nucleic acid monomers are made from a carbohydrate monosaccharide a nitrogenous base and one or more high energy phosphate groups . When joined together they form either the unit of inheritance , the gene , made from DNA or RNA , which translates the genetic information into protein structures . The monomer unit of a protein is usually one of 20 amino acids , comprising an amine group , a hydrocarbon , and a carboxylic acid . Through a condensation reaction , in which the carboxylic acid of one amino acid is linked to the amine of another with removal of a water molecule , a peptide bond is formed . Polymers of amino acids are termed proteins and these molecules provide many catalytic metabolic functions for living processes . Any successful theory of abiogenesis must explain the origins and interactions of these five classes of molecules .   Many approaches to abiogenesis investigate how self-replicating molecules , or their components , came into existence . It is generally thought that current life on Earth is descended from an RNA world , although RNA-based life may not have been the first life to have existed . The classic Miller -- Urey experiment and similar research demonstrated that most amino acids , the basic chemical constituents of the proteins used in all living organisms , can be synthesized from inorganic compounds under conditions intended to replicate those of the early Earth . Various external sources of energy that may have triggered these reactions have been proposed , including lightning and radiation . Other approaches ( `` metabolism-first '' hypotheses ) focus on understanding how catalysis in chemical systems on the early Earth might have provided the precursor molecules necessary for self-replication . Complex organic molecules have been found in the Solar System and in interstellar space , and these molecules may have provided starting material for the development of life on Earth .   The panspermia hypothesis alternatively suggests that microscopic life was distributed to the early Earth by meteoroids , asteroids and other small Solar System bodies and that life may exist throughout the Universe . It is speculated that the biochemistry of life may have begun shortly after the Big Bang , 13.8 billion years ago , during a habitable epoch when the age of the universe was only 10 to 17 million years . The panspermia hypothesis proposes that life originated outside the Earth , not how life came to be .   Nonetheless , Earth remains the only place in the Universe known to harbour life , and fossil evidence from the Earth informs most studies of abiogenesis . More than 99 % of all species of life forms , amounting to over five billion species , that ever lived on Earth are estimated to be extinct . The age of the Earth is about 4.54 billion years ; the earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago , and possibly as early as the Eoarchean Era , after geological crust started to solidify following the molten Hadean Eon . In May 2017 , evidence of the earliest known life on land may have been found in 3.48-billion-year-old geyserite and other related mineral deposits ( often found around hot springs and geysers ) uncovered in the Pilbara Craton of Western Australia . However , there have been a number of discoveries that suggested the earliest appearance of life on Earth was even earlier in time . Currently , microfossils within hydrothermal vent precipitates dated from 3.77 to 4.28 billion years old found in Quebec , Canada may be the oldest record of life on Earth , suggesting `` an almost instantaneous emergence of life '' after ocean formation 4.4 billion years ago . According to biologist Stephen Blair Hedges , `` If life arose relatively quickly on Earth ... then it could be common in the universe . ''

negative: Madagascar Plate The Madagascar Plate or Madagascar block was once attached to the Gondwana supercontinent and later the Indo-Australian Plate .   Rifting in the Somali Basin began at the end of the Carboniferous 300 million years ago , as a part of the Karoo rift system . The initiation of Gondwana breakup , and transform faulting along the Davie Fracture Zone , occurred in the Toarcian ( about 182 million years ago ) following the eruption of the Bouvet ( Karoo ) mantle plume . At this time East Gondwana , comprising the Antarctic , Madagascar , Indian , and Australian plates , began to separate from the African Plate . East Gondwana then began to break apart about 115 -- 120 million years ago when India began to move northward . Between 84 -- 95 million years ago rifting separated Seychelles and India from Madagascar .   Since its formation the Madagascar block has moved roughly in conjunction with Africa , and thus there are questions as to whether the Madagascar Plate should be still considered a separate plate .

negative: Serotiny Serotiny is an ecological adaptation exhibited by some seed plants , in which seed release occurs in response to an environmental trigger , rather than spontaneously at seed maturation . The most common and best studied trigger is fire . However , the term serotiny refers more broadly to plants that release their seeds over a long period of time , irrespective of the trigger or whether release is spontaneous . In this sense , the term is synonymous with bradyspory .   Possible triggers include  Death of the parent plant or branch ( this death can be caused by fire ) . This form of serotiny has been termed necriscence .  Wetting ( hygriscence )  Warming by the sun ( soliscence )  Drying atmospheric conditions ( xeriscence )  Fire ( heat , essentially : pyriscence )  Fire followed by wetting ( pyrohydriscence )  Fire is the most common and best studied case . Some plants may respond to more than one of these triggers . For example Pinus halepensis exhibits primarily fire-mediated serotiny , but responds weakly to drying atmospheric conditions . Similarly , some Banksia species are strongly serotinous with respect to fire , but also release some seed in response to plant or branch death .   Serotiny can occur in various degrees . Plants that retain all of their seed indefinitely in the absence of a trigger event are strongly serotinous . Plants that eventually release some of their seed spontaneously in the absence of a trigger are weakly serotinous . Finally , some plants release all of their seed spontaneously after a period of seed storage , but the occurrence of a trigger event curtails the seed storage period , causing all seed to be released immediately ; such plants are essentially non-serotinous , or facultatively serotinous .

negative: Presbyterian Church (U.S.A.) Carbon Neutral Resolution The Presbyterian Church ( USA ) Carbon Neutral Resolution was a resolution passed at the June , 2006 , 217th General Assembly of the Presbyterian Church ( USA ) strongly urging all Presbyterians to ` immediately aspire to live carbon neutral lives ' . It is believed that resolution was the first in the world by a major religious denomination for its followers to become carbon neutral .   The resolution also directed the Advisory Committee on Social Witness Policy to make available detail of how Presbyterians could take to reduce their energy consumption and recognised that ` the Christian mandate to care for creation and the biblical promise of the restoration of right relationships between God , human beings , and the rest of creation impels and inspires Presbyterians to act to reduce -LSB- their -RSB- energy usage ' .   The resolution was based on a report by a task force prepared for the Advisory Committee on Social Witness Policy . After the Advisory Committee voted to postpone consideration of the report until the 2008 General Assembly , two General Assembly Commissioners bypassed the committee and were successful in getting the resolution adopted .   The Church first noted its ` serious concern ' over global warming at the 1990 General Assembly , when it warned that ` the global atmospheric warming trend ( the greenhouse effect ) represents one of the most serious global environmental challenges to the health , security , and stability of human life and natural ecosystems ' . Despite this , a survey carried out in 2004 revealed that over half of all Presbyterians had not taken even the ` simplest steps to decrease their energy usage ' , and that most congregations had not implemented energy conservation programs .

negative: Global warming hiatus A global warming hiatus , also sometimes referred to as a global warming pause or a global warming slowdown , is a period of relatively little change in globally averaged surface temperatures . In the current episode of global warming many such 15-year periods appear in the surface temperature record , along with robust evidence of the long-term warming trend ; climate is classically averaged over 30-year periods .   Publicity has surrounded claims of a global warming hiatus during the period 1998 -- 2013 . The exceptionally warm El Niño year of 1998 was an outlier from the continuing temperature trend , and so subsequent annual temperatures gave the appearance of a hiatus : by January 2006 , it appeared to some that global warming had stopped or paused . A 2009 study showed that decades without warming were not exceptional , and in 2011 a study showed that if allowances were made for known variability , the rising temperature trend continued unabated . There was increased public interest in 2013 in the run-up to publication of the IPCC Fifth Assessment Report , and despite concerns that a 15-year period was too short to determine a meaningful trend , the IPCC included a section on a hiatus , which it defined as a much smaller increasing linear trend over the 15 years from 1998 to 2012 , than over the 60 years from 1951 to 2012 . Various studies examined possible causes of the short-term slowdown . Even though the overall climate system has continued to accumulate energy due to Earth 's positive energy budget , the available temperature readings at the Earth 's surface indicate slower rates of increase in surface warming than in the prior decade . Since measurements at the top of the atmosphere show that Earth is receiving more energy than it is radiating back into space , the retained energy should be producing warming in the Earth 's climate system .   Research reported in July 2015 on an updated NOAA dataset casts doubt on the existence of a hiatus , and it finds no indication of a slowdown even in earlier years . Scientists working on other datasets welcomed this study , though they have expressed the view that the recent warming trend was less than in previous periods of the same length . Subsequently , a detailed study supports the conclusion that warming is continuing , but it also find there was less warming between 2001 and 2010 than climate models had predicted , and that this slowdown might be attributed to short-term variations in the Pacific decadal oscillation ( PDO ) , which was negative during that period . Another review finds `` no substantive evidence '' of a pause in global warming . A statistical study of global temperature data since 1970 concludes that the term ` hiatus ' or ` pause ' is not justified .   Independent of these discussions about data and measurements for earlier years , 2015 turned out to be much warmer than any of the earlier years , already before El Niño conditions started . The warmth of 2015 largely ended any remaining scientific credibility of claims that the supposed `` hiatus '' since 1998 had any significance for the long-term warming trend . In January 2017 , a study published in the journal Science Advances cast further doubt on the existence of a recent pause , with more evidence that ocean temperatures have been underestimated . An April 2017 study found the data consistent with a steady warming trend globally since the 1970s , with fluctuations within the expected range of short term variability .