query: Internal variability can only account for small amounts of warming and cooling over periods of decades, and scientific studies have consistently shown that it cannot account for the global warming over the past century.

positive: Attribution of recent climate change Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for recent climate changes on Earth , commonly known as ` global warming ' . The effort has focused on changes observed during the period of instrumental temperature record , when records are most reliable ; particularly in the last 50 years , when human activity has grown fastest and observations of the troposphere have become available . The dominant mechanisms are anthropogenic , i.e. , the result of human activity . They are :  increasing atmospheric concentrations of greenhouse gases  global changes to land surface , such as deforestation  increasing atmospheric concentrations of aerosols .   There are also natural mechanisms for variation including climate oscillations , changes in solar activity , and volcanic activity .   According to the Intergovernmental Panel on Climate Change ( IPCC ) , it is `` extremely likely '' that human influence was the dominant cause of global warming between 1951 and 2010 . The IPCC defines `` extremely likely '' as indicating a probability of 95 to 100 % , based on an expert assessment of all the available evidence .   Multiple lines of evidence support attribution of recent climate change to human activities :  A basic physical understanding of the climate system : greenhouse gas concentrations have increased and their warming properties are well-established .  Historical estimates of past climate changes suggest that the recent changes in global surface temperature are unusual .  Computer-based climate models are unable to replicate the observed warming unless human greenhouse gas emissions are included .  Natural forces alone ( such as solar and volcanic activity ) can not explain the observed warming .   The IPCC 's attribution of recent global warming to human activities is a view shared by the scientific community , and is also supported by 196 other scientific organizations worldwide ( see also : scientific opinion on climate change ) .

positive: 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 .

positive: Little Ice Age The Little Ice Age ( LIA ) was a period of cooling that occurred after the Medieval Warm Period . Although it was not a true ice age , the term was introduced into scientific literature by François E. Matthes in 1939 . It has been conventionally defined as a period extending from the 16th to the 19th centuries , but some experts prefer an alternative timespan from about 1300 to about 1850 . Climatologists and historians working with local records no longer expect to agree on either the start or end dates of the period , which varied according to local conditions .   The NASA Earth Observatory notes three particularly cold intervals : one beginning about 1650 , another about 1770 , and the last in 1850 , all separated by intervals of slight warming . The Intergovernmental Panel on Climate Change Third Assessment Report considered the timing and areas affected by the Little Ice Age suggested largely-independent regional climate changes rather than a globally-synchronous increased glaciation . At most , there was modest cooling of the Northern Hemisphere during the period .   Several causes have been proposed : cyclical lows in solar radiation , heightened volcanic activity , changes in the ocean circulation , variations in Earth 's orbit and axial tilt ( orbital forcing ) , inherent variability in global climate , and decreases in the human population .

positive: Global warming Global warming , also referred to as climate change , is the observed century-scale rise in the average temperature of the Earth 's climate system and its related effects . Multiple lines of scientific evidence show that the climate system is warming . Many of the observed changes since the 1950s are unprecedented in the instrumental temperature record which extends back to the mid 19th century , and in paleoclimate proxy records over thousands of years .   In 2013 , the Intergovernmental Panel on Climate Change ( IPCC ) Fifth Assessment Report concluded that `` It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century . '' The largest human influence has been emission of greenhouse gases such as carbon dioxide , methane and nitrous oxide . Climate model projections summarized in the report indicated that during the 21st century the global surface temperature is likely to rise a further 0.3 to for their lowest emissions scenario and 2.6 to for the highest emissions scenario . These findings have been recognized by the national science academies of the major industrialized nations and are not disputed by any scientific body of national or international standing .   Future climate change and associated impacts will differ from region to region around the globe . Anticipated effects include warming global temperature , rising sea levels , changing precipitation , and expansion of deserts in the subtropics . Warming is expected to be greater over land than over the oceans and greatest in the Arctic , with the continuing retreat of glaciers , permafrost and sea ice . Other likely changes include more frequent extreme weather events including heat waves , droughts , heavy rainfall with floods and heavy snowfall ; ocean acidification ; and species extinctions due to shifting temperature regimes . Effects significant to humans include the threat to food security from decreasing crop yields and the abandonment of populated areas due to rising sea levels . Because the climate system has a large `` inertia '' and greenhouse gases will stay in the atmosphere for a long time , many of these effects will not only exist for decades or centuries , but will persist for tens of thousands of years .   Possible societal responses to global warming include mitigation by emissions reduction , adaptation to its effects , building systems resilient to its effects , and possible future climate engineering . Most countries are parties to the United Nations Framework Convention on Climate Change ( UNFCCC ) ,  whose ultimate objective is to prevent dangerous anthropogenic climate change . Parties to the UNFCCC have agreed that deep cuts in emissions are required and that global warming should be limited to well below 2.0 C-change relative to pre-industrial levels , with efforts made to limit warming to 1.5 C-change .   Public reactions to global warming and concern about its effects are also increasing . A global 2015 Pew Research Center report showed a median of 54 % consider it `` a very serious problem '' . There are significant regional differences , with Americans and Chinese ( whose economies are responsible for the greatest annual CO2 emissions ) among the least concerned .

negative: Global warming controversy The global warming controversy concerns the public debate over whether global warming is occurring , how much has occurred in modern times , what has caused it , what its effects will be , whether any action should be taken to curb it , and if so what that action should be . In the scientific literature , there is a strong consensus that global surface temperatures have increased in recent decades and that the trend is caused by human-induced emissions of greenhouse gases . No scientific body of national or international standing disagrees with this view , though a few organizations with members in extractive industries hold non-committal positions . Disputes over the key scientific facts of global warming are more prevalent in the media than in the scientific literature , where such issues are treated as resolved , and such disputes are more prevalent in the United States than globally .   Political and popular debate concerning the existence and cause of climate change includes the reasons for the increase seen in the instrumental temperature record , whether the warming trend exceeds normal climatic variations , and whether human activities have contributed significantly to it . Scientists have resolved these questions decisively in favour of the view that the current warming trend exists and is ongoing , that human activity is the cause , and that it is without precedent in at least 2000 years . Public disputes that also reflect scientific debate include estimates of how responsive the climate system might be to any given level of greenhouse gases ( climate sensitivity ) , how global climate change will play out at local and regional scales , and what the consequences of global warming will be .   Global warming remains an issue of widespread political debate , often split along party political lines , especially in the United States . Many of the issues that are settled within the scientific community , such as human responsibility for global warming , remain the subject of politically or economically motivated attempts to downplay , dismiss or deny them -- an ideological phenomenon categorised by academics and scientists as climate change denial . The sources of funding for those involved with climate science -- both supporting and opposing mainstream scientific positions -- have been questioned by both sides . There are debates about the best policy responses to the science , their cost-effectiveness and their urgency . Climate scientists , especially in the United States , have reported official and oil-industry pressure to censor or suppress their work and hide scientific data , with directives not to discuss the subject in public communications . Legal cases regarding global warming , its effects , and measures to reduce it have reached American courts . The fossil fuels lobby has been identified as overtly or covertly supporting efforts to undermine or discredit the scientific consensus on global warming .

negative: Scientific consensus on climate change There is currently a strong scientific consensus that the Earth is warming and that this warming is mainly caused by human activities. This consensus is supported by various studies of scientists' opinions and by position statements of scientific organizations, many of which explicitly agree with the Intergovernmental Panel on Climate Change (IPCC) synthesis reports.  Nearly all actively publishing climate scientists (97–98%) support the consensus on anthropogenic climate change, and the remaining 2% of contrarian studies either cannot be replicated or contain errors.

negative: Climate of Adelaide Adelaide has a Mediterranean climate ( Köppen climate classification Csa ) , with mild to cool winters with moderate rainfall and warm to hot , dry summers .   Adelaide is the driest of the Australian capital cities and the past two decades have been far warmer than usual , with the past 8 years seeing an excess of 40 + degrees every summer . Alarmingly , the city has also recorded almost 10 consecutive years of below-average Spring rainfall , with 2014 on track to continuing this trend .   A spike in heat waves , droughts and record-breaking high temperatures over the past decade has led to some concerns over the effects of global warming and Man-made climate change ( AGW ) on the city . Nine of the ten warmest years recorded in Adelaide have occurred since 2002 , with 2013 being the hottest year and summer 2015 -- 2016 being the fourth-hottest summer recorded .

negative: Drought in Australia Drought in Australia is defined by the Australian Bureau of Meteorology as rainfall over a three-month period being in the lowest decile of what has been recorded for that region in the past . This definition takes into account that drought is a relative term and rainfall deficiencies need to be compared to typical rainfall patterns including seasonal variations . Specifically drought in Australia is defined in relation to a rainfall deficiency of pastoral leases and is determined by decile analysis applied to a certain area . Note that this definition uses rainfall only because long-term records are widely available across most of Australia . However , it does not take into account other variables that might be important for establishing surface water balance , such as evaporation and condensation .   Historical climatic records are now sufficiently reliable to profile climate variability taking into account expectations for regions . Bureau of Meteorology records since the 1860s show that a ` severe ' drought has occurred in Australia , on average , once every 18 years . State Governments are responsible for declaring a region drought affected and the declaration will take into account factors other than rainfall .   The worst drought to affect the country occurred in the 21st century -- between the years 2003 to 2012 . Nonetheless , many regions of Australia are still in significant drought and rainfall records have showed a marked decrease in precipitation levels since 1994 , with many scientists attributing this to climate change and global warming . Deficiencies in northern Australia increased in 2013 -- 14 , leading to an extended drought period in certain parts of Queensland .

negative: IPCC First Assessment Report The First Assessment Report ( FAR ) of the Intergovernmental Panel on Climate Change ( IPCC ) was completed in 1990 . It served as the basis of the United Nations Framework Convention on Climate Change ( UNFCCC ) .   The report was issued in three main sections , corresponding to the three Working Groups of scientists that the IPCC had established .   Working Group I : Scientific Assessment of Climate Change , edited by J.T. Houghton , G.J. Jenkins and J.J. Ephraums  Working Group II : Impacts Assessment of Climate Change , edited by W.J. McG . Tegart , G.W. Sheldon and D.C. Griffiths  Working Group III : The IPCC Response Strategies   Each section included a summary for policymakers . This format was followed in subsequent Assessment Reports .   The executive summary of the policymakers ' summary of the WG I report includes :   We are certain of the following : there is a natural greenhouse effect ... ; emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases : CO2 , methane , CFCs and nitrous oxide . These increases will enhance the greenhouse effect , resulting on average in an additional warming of the Earth 's surface . The main greenhouse gas , water vapour , will increase in response to global warming and further enhance it .  We calculate with confidence that : ... CO2 has been responsible for over half the enhanced greenhouse effect ; long-lived gases would require immediate reductions in emissions from human activities of over 60 % to stabilise their concentrations at today 's levels ...  Based on current models , we predict : under -LSB- BAU -RSB- increase of global mean temperature during the -LSB- 21st -RSB- century of about 0.3 oC per decade ( with an uncertainty range of 0.2 to 0.5 oC per decade ) ; this is greater than that seen over the past 10,000 years ; under other ... scenarios which assume progressively increasing levels of controls , rates of increase in global mean temperature of about 0.2 oC -LSB- to -RSB- about 0.1 oC per decade .  There are many uncertainties in our predictions particularly with regard to the timing , magnitude and regional patterns of climate change , due to our incomplete understanding of : sources and sinks of GHGs ; clouds ; oceans ; polar ice sheets .  Our judgement is that : global mean surface air temperature has increased by 0.3 to 0.6 oC over the last 100 years ... ; The size of this warming is broadly consistent with predictions of climate models , but it is also of the same magnitude as natural climate variability . Thus the observed increase could be largely due to this natural variability ; alternatively this variability and other human factors could have offset a still larger human-induced greenhouse warming . The unequivocal detection of the enhanced greenhouse effect is not likely for a decade or more .  under the IPCC business as usual emissions scenario , an average rate of global mean sea level rise of about 6 cm per decade over the next century ( with an uncertainty range of 3 -- 10 cm per decade ) , mainly due to thermal expansion of the oceans and the melting of some land ice . The predicted rise is about 20 cm ... by 2030 , and 65 cm by the end of the next century .

negative: Scientific opinion on climate change The scientific opinion on climate change is the overall judgment among scientists regarding the extent to which global warming is occurring , its causes , and its probable consequences . The scientific consensus is that the Earth 's climate system is unequivocally warming , and that it is extremely likely ( meaning 95 % probability or higher ) that this warming is predominantly caused by humans . It is likely that this mainly arises from increased concentrations of greenhouse gases in the atmosphere , such as from deforestation and the burning of fossil fuels , partially offset by human caused increases in aerosols ; natural changes had little effect .   This scientific opinion is expressed in synthesis reports , by scientific bodies of national or international standing , and by surveys of opinion among climate scientists . Individual scientists , universities , and laboratories contribute to the overall scientific opinion via their peer-reviewed publications , and the areas of collective agreement and relative certainty are summarised in these respected reports and surveys .   National and international science academies and scientific societies have assessed current scientific opinion on global warming . These assessments are generally consistent with the conclusions of the Intergovernmental Panel on Climate Change . The IPCC Fourth Assessment Report stated that :  Warming of the climate system is unequivocal , as evidenced by increases in global average air and ocean temperatures , the widespread melting of snow and ice , and rising global average sea level .  Most of the global warming since the mid-20th century is very likely due to human activities .  Benefits and costs of climate change for -LSB- human -RSB- society will vary widely by location and scale . Some of the effects in temperate and polar regions will be positive and others elsewhere will be negative . Overall , net effects are more likely to be strongly negative with larger or more rapid warming .  The range of published evidence indicates that the net damage costs of climate change are likely to be significant and to increase over time .  The resilience of many ecosystems is likely to be exceeded this century by an unprecedented combination of climate change , associated disturbances ( e.g. flooding , drought , wildfire , insects , ocean acidification ) and other global change drivers ( e.g. land-use change , pollution , fragmentation of natural systems , over-exploitation of resources ) .   Some scientific bodies have recommended specific policies to governments , and science can play a role in informing an effective response to climate change . Policy decisions , however , may require value judgements and so are not included in the scientific opinion .   No scientific body of national or international standing maintains a formal opinion dissenting from any of these main points . The last national or international scientific body to drop dissent was the American Association of Petroleum Geologists , which in 2007 updated its statement to its current non-committal position . Some other organizations , primarily those focusing on geology , also hold non-committal positions .

negative: Cooling down Cooling down ( the prescribed event of which is called a cool down , cooldown , or cool-down ; or warm down , in allusion to use in combination with warm up ) is an easy exercise , done after a more intense activity , to allow the body to gradually transition to a resting or near-resting state . Depending on the intensity of the exercise , cooling down can involve a slow jog or walk . With lower intensities stretching can be used . Cooling down allows the heart rate to return to its resting rate . Anecdotally cooling down may reduce dizziness for professional or serious athletes and vocal performers after strenuous workouts . Studies are currently inconclusive as to whether the process actually reduces delayed-onset muscle soreness and muscle soreness not caused by lactate production during intense exercise . Some have shown a weak correlation : however , the majority of recent studies discount the relationship . One study has shown that athletes who perform an appropriate cool-down are less likely to become injured .

negative: Hockey stick graph Hockey stick graphs present the global or hemispherical mean temperature record of the past 500 to 2000 years as shown by quantitative climate reconstructions based on climate proxy records . These reconstructions have consistently shown a slow long term cooling trend changing into relatively rapid warming in the 20th century , with the instrumental temperature record by 2000 exceeding earlier temperatures .   The term `` hockey stick graph '' was coined by the climatologist Jerry Mahlman , to describe the pattern shown by the ( MBH99 ) reconstruction , envisaging a graph that is relatively flat with a downward trend to 1900 as forming an ice hockey stick 's `` shaft '' followed by a sharp , steady increase corresponding to the `` blade '' portion . The reconstructions have featured in Intergovernmental Panel on Climate Change ( IPCC ) reports as evidence of global warming . Arguments over the reconstructions have been taken up by fossil fuel industry funded lobbying groups attempting to cast doubt on climate science .   Paleoclimatology dates back to the 19th century , and the concept of examining varves in lake beds and tree rings to track local climatic changes was suggested in the 1930s . In the 1960s , Hubert Lamb generalised from historical documents and temperature records of central England to propose a Medieval Warm Period from around 900 to 1300 , followed by Little Ice Age . This was the basis of a `` schematic diagram '' featured in the IPCC First Assessment Report of 1990 beside cautions that the medieval warming might not have been global . The use of indicators to get quantitative estimates of the temperature record of past centuries was developed , and by the late 1990s a number of competing teams of climatologists found indications that recent warming was exceptional . introduced the `` Composite Plus Scaling '' ( CPS ) method used by most later large scale reconstructions . Their study was featured in the IPCC Second Assessment Report of 1995 .   In 1998 Michael E. Mann , Raymond S. Bradley and Malcolm K. Hughes developed new statistical techniques to produce ( MBH98 ) , the first eigenvector-based climate field reconstruction ( CFR ) . This showed global patterns of annual surface temperature , and included a graph of average hemispheric temperatures back to 1400 with shading emphasising that uncertainties ( to two standard error limits ) were much greater in earlier centuries . independently produced a CPS reconstruction extending back for a thousand years , and ( MBH99 ) used the MBH98 methodology to extend their study back to 1000 .   A version of the MBH99 graph was featured prominently in the 2001 IPCC Third Assessment Report ( TAR ) , which also drew on Jones et al. 1998 and three other reconstructions to support the conclusion that , in the Northern Hemisphere , the 1990s was likely to have been the warmest decade and 1998 the warmest year during the past 1,000 years . The graph became a focus of dispute for those opposed to the strengthening scientific consensus that late 20th century warmth was exceptional . In 2003 , as lobbying over the 1997 Kyoto Protocol intensified , a paper claiming greater medieval warmth was quickly dismissed by scientists in the Soon and Baliunas controversy . Later in 2003 , Stephen McIntyre and Ross McKitrick published disputing the data used in MBH98 paper . In 2004 Hans von Storch published criticism of the statistical techniques as tending to underplay variations in earlier parts of the graph , though this was disputed and he later accepted that the effect was very small . In 2005 McIntyre and McKitrick published criticisms of the principal components analysis methodology as used in MBH98 and MBH99 . Their analysis was subsequently disputed by published papers including and which pointed to errors in the McIntyre and McKitrick methodology . Political disputes led to the formation of a panel of scientists convened by the National Research Council , their North Report in 2006 supported Mann 's findings with some qualifications , including agreeing that there were some statistical failings but these had little effect on the result .   More than two dozen reconstructions , using various statistical methods and combinations of proxy records , support the broad consensus shown in the original 1998 hockey-stick graph , with variations in how flat the pre-20th century `` shaft '' appears . The 2007 IPCC Fourth Assessment Report cited 14 reconstructions , 10 of which covered 1,000 years or longer , to support its strengthened conclusion that it was likely that Northern Hemisphere temperatures during the 20th century were the highest in at least the past 1,300 years . Further reconstructions , including Mann et al. 2008 and , have supported these general conclusions .

negative: List of scientists opposing the mainstream scientific assessment of global warming This is a list of scientists who have made statements that conflict with the scientific consensus on global warming as summarized by the Intergovernmental Panel on Climate Change and endorsed by other scientific bodies . As approximately 97 % of publishing climate scientists support the consensus on anthropogenic climate change , this list represents a minority viewpoint .   The scientific consensus is that the global average surface temperature has risen over the last century . Scientific opinion on climate change was summarized in the 2001 Third Assessment Report of the Intergovernmental Panel on Climate Change ( IPCC ) . The main conclusions on global warming at that time were as follows :  The global average surface temperature has risen 0.6 ± 0.2 ° C since the late 19th century , and 0.17 ° C per decade in the last 30 years .  `` There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities '' , in particular emissions of the greenhouse gases carbon dioxide and methane .  If greenhouse gas emissions continue the warming will also continue , with temperatures projected to increase by 1.4 ° C to 5.8 ° C between 1990 and 2100 . Accompanying this temperature increase will be increases in some types of extreme weather and a projected sea level rise . The balance of impacts of global warming become significantly negative at larger values of warming .   These findings are recognized by the national science academies of all the major industrialized nations ; the consensus has strengthened over time and is now virtually unanimous . The level of consensus correlates with expertise in climate science .   There have been several efforts to compile lists of dissenting scientists , including a 2008 US senate minority report , the Oregon Petition , and a 2007 list by the Heartland Institute , all three of which have been criticized on a number of grounds .   For the purpose of this list , a `` scientist '' is defined as an individual who has published at least one peer-reviewed research article in the broad field of natural sciences , although not necessarily in a field relevant to climatology . Since the publication of the IPCC Third Assessment Report , each has made a clear statement in his or her own words ( as opposed to the name being found on a petition , etc. ) disagreeing with one or more of the report 's three main conclusions . Their views on climate change are usually described in more detail in their biographical articles . Few of the statements in the references for this list are part of the peer-reviewed scientific literature ; most are from other sources such as interviews , opinion pieces , online essays and presentations .   NB : Only individuals who have their own Wikipedia article may be included in the list .

negative: Hurricane Alley Hurricane Alley is an area of warm water in the Atlantic Ocean stretching from the west coast of northern Africa to the east coast of Central America and Gulf Coast of the Southern United States . Many hurricanes form within this area . The sea surface temperature of the Atlantic in Hurricane Alley has been steadily growing warmer over the past decades , which most climate scientists believe accounts for the increase in hurricane activity .

negative: Satellite temperature measurements The temperature of the atmosphere at various altitudes as well as sea and land surface temperatures can be inferred from satellite measurements . These measurements can be used to locate weather fronts , monitor the El Niño-Southern Oscillation , determine the strength of tropical cyclones , study urban heat islands and monitor the global climate . Wildfires , volcanos , and industrial hot spots can also be found via thermal imaging from weather satellites .   Weather satellites do not measure temperature directly . They measure radiances in various wavelength bands . Since 1978 microwave sounding units ( MSUs ) on National Oceanic and Atmospheric Administration polar orbiting satellites have measured the intensity of upwelling microwave radiation from atmospheric oxygen , which is related to the temperature of broad vertical layers of the atmosphere . Measurements of infrared radiation pertaining to sea surface temperature have been collected since 1967 .   Satellite datasets show that over the past four decades the troposphere has warmed and the stratosphere has cooled . Both of these trends are consistent with the influence of increasing atmospheric concentrations of greenhouse gases .

negative: Ocean heat content Oceanic heat content ( OHC ) is the heat stored in the ocean . Oceanography and climatology are the science branches which study ocean heat content . Changes in the ocean heat content play an important role in the sea level rise , because of thermal expansion . It is with high confidence that ocean warming accounts for 90 % of the energy accumulation from global warming between 1971 and 2010 .

negative: Economics of global warming The economics of global warming concerns the economic aspects of global warming ; this can inform policies that governments might consider in response . A number of factors make this a difficult problem from both economic and political perspectives : it is a long-term , intergenerational problem ; benefits and costs are distributed unequally both within and across countries ; and scientific and public opinions may diverge .   One of the most important greenhouse gases is carbon dioxide . Around 20 % of carbon dioxide which is emitted due to human activities can remain in the atmosphere for many thousands of years . The long time scales and uncertainty associated with global warming have led analysts to develop `` scenarios '' of future environmental , social and economic changes . These scenarios can help governments understand the potential consequences of their decisions .   The impacts of climate change include the loss of biodiversity , sea level rise , increased frequency and severity of some extreme weather events , and acidification of the oceans . Economists have attempted to quantify these impacts in monetary terms , but these assessments can be controversial .   The two main policy responses to global warming are to reduce greenhouse gas emissions ( climate change mitigation ) and to adapt to the impacts of global warming ( e.g. , by building levees in response to sea level rise ) . Another policy response which has recently received greater attention is geoengineering of the climate system ( e.g. injecting aerosols into the atmosphere to reflect sunlight away from the Earth 's surface ) .   One of the responses to the uncertainties of global warming is to adopt a strategy of sequential decision making . This strategy recognizes that decisions on global warming need to be made with incomplete information , and that decisions in the near term will have potentially long-term impacts . Governments might choose to use risk management as part of their policy response to global warming . For instance , a risk-based approach can be applied to climate impacts which are difficult to quantify in economic terms , e.g. , the impacts of global warming on indigenous peoples .   Analysts have assessed global warming in relation to sustainable development . Sustainable development considers how future generations might be affected by the actions of the current generation . In some areas , policies designed to address global warming may contribute positively towards other development objectives . In other areas , the cost of global warming policies may divert resources away from other socially and environmentally beneficial investments ( the opportunity costs of climate change policy ) .

negative: Temperature record of the past 1000 years For information on the description of the Medieval Warm Period and Little Ice Age in various IPCC reports see MWP and LIA in IPCC reportsThe temperature record of the past 1,000 years is reconstructed using data from climate proxy records in conjunction with the modern instrumental temperature record which only covers the last 150 years at a global scale . Large-scale reconstructions covering part or all of the 1st millennium and 2nd millennium have shown that recent temperatures are exceptional : the Intergovernmental Panel on Climate Change Fourth Assessment Report of 2007 concluded that `` Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely '' the highest in at least the past 1,300 years . '' The curve shown in graphs of these reconstructions is widely known as the hockey stick graph because of the sharp increase in temperatures during the last century . As of 2010 this broad pattern was supported by more than two dozen reconstructions , using various statistical methods and combinations of proxy records , with variations in how flat the pre-20th-century `` shaft '' appears . Sparseness of proxy records results in considerable uncertainty for earlier periods .   Individual proxy records , such as tree ring widths and densities used in dendroclimatology , are calibrated against the instrumental record for the period of overlap . Networks of such records are used to reconstruct past temperatures for regions : tree ring proxies have been used to reconstruct Northern Hemisphere extratropical temperatures ( within the tropics trees do not form rings ) but are confined to land areas and are scarce in the Southern Hemisphere which is largely ocean . Wider coverage is provided by multiproxy reconstructions , incorporating proxies such as lake sediments , ice cores and corals which are found in different regions , and using statistical methods to relate these sparser proxies to the greater numbers of tree ring records . The `` Composite Plus Scaling '' ( CPS ) method is widely used for large-scale multiproxy reconstructions of hemispheric or global average temperatures ; this is complemented by Climate Field Reconstruction ( CFR ) methods which show how climate patterns have developed over large spatial areas , making the reconstruction useful for investigating natural variability and long-term oscillations as well as for comparisons with patterns produced by climate models .   During the 1,900 years before the 20th century , it is likely that the next warmest period was from 950 to 1100 , with peaks at different times in different regions . This has been called the Medieval Warm Period , and some evidence suggests widespread cooler conditions during a period around the 17th century known as the Little Ice Age . In the hockey stick controversy , contrarians have asserted that the Medieval Warm Period was warmer than at present , and have disputed the data and methods of climate reconstructions .

negative: Crowe Horwath International Crowe Horwath International is a network of accounting and advisory services firms . Crowe Horwath International is ranked among the top 10 global accounting networks . The network consists of 752 offices with over 33,207 employees in 130 countries .

negative: Steam devil A steam devil is a small , weak whirlwind over water ( or sometimes wet land ) that has drawn fog into the vortex , thus rendering it visible .   They form over large lakes and oceans during cold air outbreaks while the water is still relatively warm , and can be an important mechanism in vertically transporting moisture . They are a component of sea smoke .   Smaller steam devils and steam whirls can form over geyser basins even in warm weather because of the very high water temperatures . Although observations of steam devils are generally quite rare , hot springs in Yellowstone Park produce them on a daily basis .   Steam devils have only been reported and studied since the 1970s . They are weaker than waterspouts and distinct from them . The latter are more akin to weak tornadoes over water .

negative: Sea surface temperature Sea surface temperature ( SST ) is the water temperature close to the ocean 's surface . The exact meaning of surface varies according to the measurement method used , but it is between 1 mm and 20 m below the sea surface . Air masses in the Earth 's atmosphere are highly modified by sea surface temperatures within a short distance of the shore . Localized areas of heavy snow can form in bands downwind of warm water bodies within an otherwise cold air mass . Warm sea surface temperatures are known to be a cause of tropical cyclogenesis over the Earth 's oceans . Tropical cyclones can also cause a cool wake , due to turbulent mixing of the upper 30 m of the ocean . SST changes diurnally , like the air above it , but to a lesser degree . There is less SST variation on breezy days than on calm days . In addition , ocean currents such as the Atlantic Multidecadal Oscillation ( AMO ) , can effect SST 's on multi-decadal time scales , a major impact results from the global thermohaline circulation , which affects average SST significantly throughout most of the world 's oceans .   Coastal SSTs can cause offshore winds to generate upwelling , which can significantly cool or warm nearby landmasses , but shallower waters over a continental shelf are often warmer . Onshore winds can cause a considerable warm-up even in areas where upwelling is fairly constant , such as the northwest coast of South America . Its values are important within numerical weather prediction as the SST influences the atmosphere above , such as in the formation of sea breezes and sea fog . It is also used to calibrate measurements from weather satellites .

negative: David Legates David Russell Legates is a Professor of Geography at the University of Delaware . He is the former Director of the Center for Climatic Research at the same university ,  and a former Delaware State Climatologist .   Legates has published research papers , opinion editorials , and spoken openly in opposition to the consensus scientific opinion on climate change . More recently , he has been known for his skepticism toward the anthropogenic cause of the observed global warming patterns and the severity of its consequences at the local geographical scale .   Legates viewpoint , as stated in a 2015 study that he co-authored , is that the Earth will experience about 1.0 C warming over the 2000 to 2100 period .

negative: Bølling-Allerød warming The Bølling-Allerød interstadial was an abrupt warm and moist interstadial period that occurred during the final stages of the last glacial period . This warm period ran from c. 14,700 to c. 12,700 years before the present ( BP ) . It began with the end of the cold period known as the Oldest Dryas , and ended abruptly with the onset of the Younger Dryas , a cold period that reduced temperatures back to near-glacial levels within a decade .   In some regions , a cold period known as the Older Dryas can be detected in the middle of the Bølling-Allerød interstadial . In these regions the period is divided into the Bølling oscillation , which peaked around 14,500 BP , and the Allerød oscillation , which peaked closer to 13,000 BP .   Estimates of CO2 rise are 20 -- 35 ppmv within 200 years , a rate less than 29 -- 50 % compared to the anthropogenic global warming signal from the past 50 years , and with a radiative forcing of 0.59 -- 0.75 W m − 2 .

negative: Mitigation of global warming in Australia Mitigation of global warming involves taking actions to reduce greenhouse gas emissions and to enhance sinks aimed at reducing the extent of global warming . This is in distinction to adaptation to global warming , which involves taking action to minimise the effects of global warming . Scientific consensus on global warming , together with the precautionary principle and the fear of non-linear climate transitions , is leading to increased effort to develop new technologies and sciences and carefully manage others in an attempt to mitigate global warming .   Carbon capture and storage ( CCS ) for coal-fired power stations has been put forward as a solution to rising greenhouse gas emissions . However , CCS can not deliver in time to avoid dangerous increases in temperatures , as widespread commercial use of CCS is not expected before 2030 .   Following the introduction of government mandatory renewable energy targets , more opportunities have opened up for renewable energy technologies such as wind power , photovoltaics , and solar thermal technologies . The deployment of these technologies provides opportunities for mitigating greenhouse gases .   A carbon price was introduced on 1 July 2012 by the government of Julia Gillard with the purpose of reducing Australia 's carbon emissions . It requires large businesses ( defined as those with annual carbon dioxide equivalent emissions over 25,000 tonnes annually ) to pay a price for emissions permits . The tax was scrapped by the Abbott government in July 2014 in what was a widely criticised and highly publicised move .

negative: Everything's Cool (film) Everything 's Cool is a 2007 documentary film that examines the divide between scientists and the general populace on the topic of global warming . Director Dan Gold said of the motivation for the film that `` I 'm optimistic that finally the message that this is real , that human beings are the cause of the most recent warming trend , and that it 's an important issue , that message is actually reaching America . On the other hand ... if that message was fully understood , we would be moving a lot faster to slow this down and to reverse this course . ''   The documentary was shown at the Sundance film festival in January 2007 and at the San Francisco International Film Festival in May 2007 . The directors also took Blue Vinyl , a film about plastic pollution , to Sundance in 2002 . It was shown on CBC in Canada as part of the Passionate Eye series .   The New York Times called it `` a breezy polemic about the politics of global warming ... -LSB- that -RSB- adopts a cheerful comic tone to avoid scaring audiences . '' The LA Times said that `` With wit and passion , Gold and Helfand marshal a plethora of data and developments yet never lose their narrative thread . '' . The New York Sun was less favourable , calling it `` the best movie I 've ever seen about global warming for kids in junior high school , but it 's the most annoying movie about global warming I 've ever seen for adults . ''

negative: Volcanic winter A volcanic winter is a reduction in global temperatures caused by volcanic ash and droplets of sulfuric acid and water obscuring the Sun and raising Earth 's albedo ( increasing the reflection of solar radiation ) after a large particularly explosive volcanic eruption . Long-term cooling effects are primarily dependent upon injection of sulfur gasses into the stratosphere where they undergo a series of reactions to create sulfuric acid which can nucleate and form aerosols . Volcanic stratospheric aerosols cool the surface by reflecting solar radiation and warm the stratosphere by absorbing terrestrial radiation . The volcanic aerosols , resulting from the 1991 Pinatubo eruption and others , have been shown to contribute to anthropogenic ozone depletion . The variations in atmospheric warming and cooling results in changes in tropospheric and stratospheric circulation .

negative: Ice-sheet model In climate modelling , Ice-sheet models use numerical methods to simulate the evolution , dynamics and thermodynamics of ice sheets , such as the Greenland ice sheet , the Antarctic ice sheet or the large ice sheets on the northern hemisphere during the last glacial period . They are used for a variety of purposes , from studies of the glaciation of Earth over glacial -- interglacial cycles in the past to projections of ice-sheet decay under future global warming conditions .

negative: Center for the Study of Carbon Dioxide and Global Change The Center for the Study of Carbon Dioxide and Global Change is a 501 ( c ) ( 3 ) non-profit organization based in Tempe , Arizona . The Center produces a weekly online science newsletter called CO2Science .   The Center was founded and is run by Craig D. Idso , along with Sherwood B. Idso , his father , and Keith E. Idso , his brother . They came from backgrounds in agriculture and climate . According to the Idsos , they became involved in the global warming controversy through their study of earth 's temperature sensitivity to radiative perturbations and plant responses to elevated CO2 levels and carbon sequestration . The Center sharply disputes the consensus scientific opinion on climate change shown in IPCC assessment reports , and believes that global warming will be beneficial to mankind .

negative: Cool Earth Cool Earth is a UK-based international NGO that protects endangered rainforest in order to combat global warming , protect ecosystems and to provide employment for local people .   The organisation receives its income through business partnerships , trust funds and individual contributions from over 50,000 sponsors in order to secure specific tracts of endangered rainforest . Through the Cool Earth website , an individual can donate to support indigenous communities to protect their rainforest . Less than 10 % of Cool Earth 's supporter income is spent on administration .   In 2015 , it was named Charity of the Year in its category at the Civil Society Media Charity Awards and best International NGO at the PEA Awards . It is supported by various celebrities including Professor James Lovelock , Vivienne Westwood , Ricky Gervais and Sir David Attenborough .

negative: An Appeal to Reason An Appeal to Reason : A Cool Look at Global Warming is a 2008 book by Nigel Lawson . In it , Lawson argues that global warming is happening , but that the science is far from settled . He opposes the scientific consensus as summarized by the IPCC . He also argues that warming will bring both benefits and negative consequences , and that the impact of these changes will be relatively moderate rather than apocalyptic . He criticizes politicians and scientists who predict catastrophe unless urgent action is taken , and he calls for gradual adaptation instead . The book has been criticized by some climatologists , including IPCC authors Jean Palutikof and Robert Watson .

negative: Future sea level The rate of global mean sea-level rise ( ~ 3 mm/yr ; SLR ) has accelerated compared to the mean of the 20th century ( ~ 2 mm/yr ) , but the rate of rise is locally variable . Factors contributing to SLR include decreased global ice volume and warming of the ocean . On Greenland , the deficiency between annual ice gained and lost tripled between 1996 and 2007 . On Antarctica the deficiency increased by 75 % . Mountain glaciers are retreating and the cumulative mean thickness change has accelerated from about − 1.8 to − 4 m in 1965 to 1970 to about − 12 to − 14 m in the first decade of the 21st century . From 1961 to 2003 , ocean temperatures to a depth of 700 m increased and portions of the deeper ocean are warming .   The Intergovernmental Panel on Climate Change ( 2007 ) projected sea level would reach 0.18 to 0.59 m above present by the end of the 21st century but lacked an estimate of ice flow dynamics calving . Calving was added by Pfeffer et al. ( 2008 ) indicating 0.8 to 2 m of SLR by 2100 ( favouring the low end of this range ) . Rahmstorf ( 2007 ) estimated SLR will reach 0.5 to 1.4 m by the end of the century . Pielke ( 2008 ) points out that observed SLR has exceeded the best case projections thus far . These approximations and others indicate that global mean SLR may reach 1 m by the end of this century . However , sea level is highly variable and planners considering local impacts must take this variability into account .

negative: Storm World In his book Storm World : Hurricanes , Politics , and the Battle over Global Warming , Chris Mooney discusses tensions between two different approaches to analyzing global warming and its effect on hurricanes .

negative: Global warming conspiracy theory A global warming conspiracy theory invokes claims that scientific consensus on global warming is based on conspiracies to produce false data or suppress dissent . It is one of a number of tactics used in climate change denial to legitimize political controversy disputing this consensus .  Global warming conspiracy theorists typically allege that , through worldwide acts of professional and criminal misconduct , the science behind global warming has been invented or distorted for ideological or financial reasons , or both .

negative: Global Accounting Alliance The Global Accounting Alliance ( GAA ) is an international coalition of accounting organisations that was formed in 2006 .   The GAA aims to promote standards of quality professional services , support their members , and share information and collaborate on international accounting issues . The members of the alliance represent over 775,000 of professional accountants .   The GAA provides members with a GAA Passport which provides access to other member bodies so they can access restricted areas of the local institute website , training and development , and publications at member rates when visiting their country .

negative: Climate of the Arctic The climate of the Arctic is characterized by long , cold winters and short , cool summers . There is a large amount of variability in climate across the Arctic , but all regions experience extremes of solar radiation in both summer and winter . Some parts of the Arctic are covered by ice ( sea ice , glacial ice , or snow ) year-round , and nearly all parts of the Arctic experience long periods with some form of ice on the surface . Average January temperatures range from about − 34 ° C to 0 ° C ( − 40 to +32 ° F ) , and winter temperatures can drop below − 50 ° C ( − 58 ° F ) over large parts of the Arctic . Average July temperatures range from about − 10 to +10 ° C ( 14 to 50 ° F ) , with some land areas occasionally exceeding 30 ° C ( 86 ° F ) in summer .   The Arctic consists of ocean that is largely surrounded by land . As such , the climate of much of the Arctic is moderated by the ocean water , which can never have a temperature below − 2 ° C ( 28 ° F ) . In winter , this relatively warm water , even though covered by the polar ice pack , keeps the North Pole from being the coldest place in the Northern Hemisphere , and it is also part of the reason that Antarctica is so much colder than the Arctic . In summer , the presence of the nearby water keeps coastal areas from warming as much as they might otherwise .

negative: Hurricane Katrina and global warming The tremendous destruction caused by recent Atlantic Ocean tropical cyclones , such as Hurricanes Katrina , Wilma , and Sandy caused a substantial upsurge in interest in the subject of global warming by news media and the wider public , and concerns that global climatic change may have played a significant role in those events . Time Magazine , for example , published an article titled , `` Is Global Warming Fueling Katrina ? '' -- however , the article itself addressed hurricanes in general , rather than Katrina specifically , and was inconclusive .   Shortly after the hurricane , former Boston Globe reporter Ross Gelbspan wrote an op-ed piece for the Globe titled , `` Katrina 's Real Name '' , declaring that the hurricane 's `` real name is global warming . '' Gelbspan went on to assert :  `` Although Katrina began as a relatively small hurricane that glanced off south Florida , it was supercharged with extraordinary intensity by the relatively blistering sea surface temperatures in the Gulf of Mexico . ''  Gelbspan did not single out Katrina from other recent storms in that regard ; in the article he went on to attribute other major weather events over the preceding year to global warming , including a blizzard in Los Angeles , high winds in Scandinavia , wildfires in Spain , and a drought centered in Missouri .   Britain 's then deputy prime minister , John Prescott , has linked Katrina with global warming , and statements made shortly after the hurricane by Germany 's environment minister , Jürgen Trittin , indicate he believes that global warming is responsible for an increase in the frequency of destructive natural events .   Kerry Emanuel had recently published a paper in the journal Nature that found a good correlation between hurricane intensity and sea surface temperatures . Some journalists have claimed Emanuel 's paper concludes that the recent increase in intense Atlantic storms is due to global warming , but Emanuel stated that `` it would be absurd to attribute the Katrina disaster to global warming '' .   The Internet blog RealClimate has written that `` there is no way to prove that Katrina either was , or was not , affected by global warming '' .