Carbon dioxide is not the only greenhouse gas under fire at the COP28 climate summit in Dubai, United Arab Emirates. On 2 December, the UAE, the US and China are convening other countries for a meeting focused on methane and other “non-CO2” greenhouse gases, with announcements expected from the fossil fuel industry on cutting these emissions.
In terms of contribution to climate change, methane is the most significant of these. But other gases, such as nitrous oxide and fluorinated gases made for refrigeration, are also of concern.
How much of a problem are non-CO2 greenhouse gases?
Together, they are responsible for around a third of human-caused warming so far, and the Paris agreement climate targets won’t be reached without slashing these emissions along with CO2, says Mathijs Harmsen at Utrecht University in the Netherlands. “It doesn’t get the attention in line with the climatic impact it has.”
But there is renewed focus at COP28. “We see COP28 as a turning point” for limiting the emissions of these short-lived non-CO2 greenhouse gases, says Martina Otto, who heads the Climate and Clean Air Coalition at the UN.
What are the main non-CO2 greenhouse gases?
Methane is the non-CO2 greenhouse gas that has had the greatest effect on climate change. It is followed by nitrous oxide and manufactured fluorinated gases, or “F-gases”, which are emitted in relatively small amounts but are far more potent than CO2. Sulphur hexafluoride, for instance, which is used as an electrical insulator, has a warming effect more than 23,000 times that of CO2, gram for gram.
Methane has both natural and human-caused sources – the majority of the latter come from fossil fuel production, due to leaks from wells, coal mines, pipelines and ships. Burping cows and other livestock make up the second largest share, followed by landfills, which release methane as food and other organic matter decomposes. Warming temperatures also increase methane emissions from natural sources like wetlands and thawing permafrost. These many sources have made it challenging for researchers to zero in on exactly what has been driving a steady rise in emissions since 2007.
Nitrous oxide also has natural sources, such as wetlands. But human-caused emissions of the gas have risen since the industrial revolution, mainly due to the increasing use of nitrogen fertilisers and livestock manure.
F-gases have been manufactured for refrigeration and other applications since the early 20th century. Chlorofluorocarbons (CFCs) were widely used as a refrigerant until countries agreed in the 1987 Montreal Protocol to phase out their use due to their degrading effect on the ozone. This phase-out is expected to avoid as much as 0.5°C of warming this century, although CFCs are still illegally being produced in some countries. The most common replacement for CFCs, hydrofluorocarbons (HFCs), do not degrade the ozone, but have a warming effect that is hundreds or thousands of times more potent than CO2. In 2016, countries agreed to amend the Montreal Protocol to begin phasing out HFC’s as well.
Which of these non-CO2 gases is the biggest concern?
Methane is responsible for nearly all of the warming caused by non-CO2 gases so far, or about a quarter of overall warming. “It’s really a methane story,” says Harmsen.
Methane sticks around in the atmosphere for only around 12 years, while CO2 can remain for millennia, but the gas is around 30 times more potent than CO2. While long-lasting CO2 emissions increasingly dominate over time, dealing with methane and other non-CO2 gases has a significant near-term effect. Harmsen and his colleagues recently found that keeping global warming within Paris agreement limits would be impossible without steep reductions in these non-CO2 gases.
“You will need to go quite deep with cutting non-CO2 to think about reaching the Paris agreement targets,” says Harmsen.
What are countries doing to reduce non-CO2 greenhouse gas emissions?
At the COP26 climate summit in Glasgow in 2021, the US and the European Union launched the Global Methane Pledge, where countries promised to cut the world’s methane emissions by 30 per cent by 2030. Since then, more than 150 countries have joined the pledge. Approaches to stemming the tide include plugging leaks or stopping releases from fossil fuel production and capturing emissions from landfills, among many others.
Nitrous oxide emissions could be reduced by using fertiliser more efficiently and by adopting more sustainable modes of agriculture, for instance. And thanks to the Montreal Protocol, the F-gases are already being replaced with less harmful alternatives.
What is happening at COP28 now around non-CO2 gases?
Methane is a major focus at COP28 in Dubai. “What we see here is an evolution and sharpening of what started in Glasgow,” says Matt Watson at the Environmental Defense Fund, an environmental advocacy organisation in the US. “The companies generating emissions are being asked to step to the line and make company-specific, meaningful targets.”
A joint statement by the US and China ahead of the meeting committing to include specific targets on methane and other non-CO2 greenhouse gases has also raised hopes for a strong outcome at COP28.
In his opening address to the summit, COP president Sultan Ahmed Al Jaber called on countries to adopt net-zero methane targets. He also hinted at pledges on reducing methane from oil and gas companies expected at the summit. Though he did not name specific firms, he says these will include pledges from the nationally owned oil and gas companies responsible for the majority of emissions. “Zeroing out methane emissions would make a huge impact in the shortest time frame,” he said.
Gesi ya kaboni dioksidi (CO2) sio gesi pekee ya chafu iliyoshambuliwa katika mkutano wa hali ya hewa wa COP28 huko Dubai, UAE. "Mwezi Desemba, UAE, Marekani na China zinaitisha mkutano wa nchi nyingine kuhusu gesi ya methane na gesi nyingine zisizo za CO2 ambazo zinatarajiwa kutolewa na sekta ya mafuta ya makaa ya mawe ili kupunguza uzalishaji wa gesi hizo.""" Kwa habari ya mchango wake katika mabadiliko ya hali ya hewa, methani ndiyo yenye maana zaidi kati ya hizo. Lakini gesi nyingine, kama vile nitrous oxide na gesi zenye fluorini zinazotengenezwa kwa ajili ya baridi, pia ni zenye kuogopesha. Ni nini kinachohusika na gesi za chafu zisizo za CO2? "Hizi ni pamoja na karibu theluthi moja ya joto la binadamu hadi sasa, na malengo ya hali ya hewa ya makubaliano ya Paris hayatatimizwa bila kupunguza uzalishaji huu pamoja na CO2 ""Mathijs Harms, Mkurugenzi wa Chuo Kikuu cha Utrecht, Uholanzi, alisema." "Hata hivyo, hakuna hatua yoyote ya kisheria ambayo inaweza kuathiri hali ya hewa, na hii ni moja ya sababu za COP28.""" "Tunaona COP28 kama hatua ya kugeuka kwa kupunguza uzalishaji wa gesi hizi za kijani kibichi zisizo za CO2 za muda mfupi, ""anasema Martina Otto, ambaye anaongoza Muungano wa Hali ya Hewa na Hewa Safi katika Umoja wa Mataifa." Ni nini gesi kuu za chafu zisizo za CO2? Methane ni gesi ya chafu isiyo ya CO2 ambayo imekuwa na athari kubwa zaidi kwa mabadiliko ya hali ya hewa. "Kisha nitrous oxide na gesi za fluorine zinazozalishwa, au ""F-gesi,"" ambazo hutolewa kwa kiasi kidogo lakini zina nguvu zaidi kuliko CO2." Hexafluoride ya sulfuri, ambayo hutumiwa kama insulator ya umeme, ina athari ya joto zaidi ya mara 23,000 ya CO2 kwa gramu. Methani ina vyanzo vya asili na vya binadamu - wengi wa mwisho hutoka kwa uzalishaji wa mafuta ya makaa ya mawe, kutokana na uvujaji kutoka visima, migodi ya makaa ya mawe, mabomba na meli. Mnyama wa aina ya ng'ombe na wanyama wengine wa mifugo ndio wanaosababisha uharibifu mkubwa zaidi, ikifuatiwa na viwanja vya kuondoa taka, ambavyo hutokeza gesi ya methani wakati chakula na vitu vingine vya kikaboni vinapoharibika. Joto linalopanda pia huongeza uzalishaji wa metani kutoka vyanzo vya asili kama vile maeneo yenye unyevunyevu na barafu inayobubujika. Kwa sababu ya vyanzo vingi vya gesi, ni vigumu kwa watafiti kugundua ni nini hasa kimekuwa kikisababisha ongezeko la gesi tangu mwaka 2007. Oksidi ya nitrous pia ina vyanzo vya asili, kama vile maeneo yenye unyevunyevu. Lakini uzalishaji wa gesi hiyo unaosababishwa na binadamu umeongezeka tangu mapinduzi ya viwanda, hasa kutokana na kuongezeka kwa matumizi ya mbolea za nitrojeni na mbolea ya mifugo. Gesi za F-Gas zimetengenezwa kwa ajili ya baridi na matumizi mengine tangu mwanzo wa karne ya 20. Chlorine-fluorocarbons (CFCs) zilikuwa zinatumiwa sana kama vifaa vya baridi hadi nchi zilipokubaliana katika Mkataba wa Montreal mwaka 1987 kuondoa matumizi yao kwa sababu ya athari zao za kuharibu ozoni. Kwa hivyo, inatarajiwa kwamba hatua hii ya kuondoa itazuia joto la joto la 0.5 ° C katika karne hii, ingawa CFC bado zinatengenezwa kinyume cha sheria katika nchi zingine. Kwa sababu ya hali ya hewa, hydrofluorocarbons (HFCs) ni hatari kwa ozoni, na kwa sababu ya athari ya joto, ni mara mia moja au elfu moja zaidi ya CO2. Mwaka 2016, nchi zilikubaliana kurekebisha Itifaki ya Montreal ili kuanza kuondoa HFCs pia. Ni gesi gani isiyo ya CO2 inayosababisha wasiwasi zaidi? Methane ni wajibu kwa karibu joto zote zinazosababishwa na gesi zisizo CO2 hadi sasa, au karibu robo ya joto la jumla. "Ni kweli hadithi ya methane", anasema Harmsen. Methani huhifadhiwa katika angahewa kwa miaka 12 tu, wakati CO2 inaweza kukaa kwa maelfu ya miaka, lakini gesi hiyo ni nguvu zaidi ya CO2. Wakati uzalishaji wa CO2 wa muda mrefu unazidi kutawala kwa muda, kushughulika na methane na gesi nyingine zisizo za CO2 zina athari kubwa ya muda mfupi. Harmson na wenzake hivi karibuni waligundua kuwa kuweka ongezeko la joto duniani ndani ya mipaka ya makubaliano ya Paris ingekuwa haiwezekani bila kupunguzwa kwa gesi hizi zisizo za CO2. "Tunahitaji kwenda kina kabisa na kupunguza CO2 isiyo ya CO2 kufikiria kufikia malengo ya makubaliano ya Paris, ""Harmsen anasema." Nchi zinafanya nini kupunguza uzalishaji wa gesi za chafu zisizo za CO2? Katika mkutano wa kilele wa hali ya hewa wa COP26 huko Glasgow, Marekani na Umoja wa Ulaya walianzisha ahadi ya Global Methane, ambapo nchi ziliahidi kupunguza uzalishaji wa methane ulimwenguni kwa asilimia 30 ifikapo 2030. Tangu wakati huo, nchi zaidi ya 150 zimejiunga na ahadi hiyo. Njia za kuzuia wimbi hilo ni pamoja na kuziba uvujaji au kuzuia kutolewa kutoka kwa uzalishaji wa mafuta ya makaa ya mawe na kukamata uzalishaji kutoka kwa majumba ya taka, kati ya mengine mengi. Uzalishaji wa oksidi ya nitrous unaweza kupunguzwa kwa kutumia mbolea kwa ufanisi zaidi na kwa kupitisha njia za kilimo endelevu zaidi, kwa mfano. Na shukrani kwa Itifaki ya Montreal, gesi za F tayari zinabadilishwa na mbadala zisizo na madhara. Ni nini kinachotokea katika COP28 kuhusu gesi zisizo za CO2? Mimea ya methane ni moja ya mada kuu ya COP28 mjini Dubai. "Kile tunachokiona hapa ni mageuzi na kuimarisha kile kilichoanza Glasgow,"" anasema Matt Watson katika Mfuko wa Ulinzi wa Mazingira, shirika la utetezi wa mazingira nchini Marekani." "Makampuni yanayozalisha gesi ya kaboni yanaombwa ""kuchukua hatua na kuweka malengo ya kampuni maalum, yenye maana"" Taarifa ya pamoja ya Marekani na China kabla ya mkutano wa kujitolea kujumuisha malengo maalum ya methane na gesi nyingine zisizo za CO2 pia imeongeza matumaini ya matokeo ya nguvu katika COP28." Katika hotuba yake ya ufunguzi wa mkutano huo, Rais wa COP Sultan Ahmed Al Jaber aliwaomba nchi kupitisha malengo ya metani ya sifuri. Pia alitoa ishara ya ahadi za kupunguza methane kutoka kwa makampuni ya mafuta na gesi yanayotarajiwa kwenye mkutano huo. Ingawa hakutaja majina ya makampuni maalum, anasema haya yatatia ndani ahadi kutoka kwa makampuni ya mafuta na gesi ya kitaifa yanayohusika na uzalishaji mkubwa wa gesi. "Kupunguza uzalishaji wa methani itakuwa na athari kubwa katika muda mfupi zaidi", alisema.