WORLD CLIMATE UPDATE – IPCC AR6 2021

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 WORLD CLIMATE UPDATE – IPCC AR6 2021

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• Possible becoming actual: The report released by the Intergovernmental Panel on Climate Change (IPCC) on August 9th, the first part of the IPCC’s sixth assessment report (AR6), presents the spectacle of the possible becoming actual. The focus on the risk of continued warming makes it starker than ever before.
• Who makes these reports: The IPCC’s assessments are prepared by thousands of researchers around the world. Each assessment consists of huge volumes produced by three different working groups - (a) one looks at the current state of the physical science of climate change, (b) the second assesses research on impacts, vulnerability and adaptation, and (c) the third looks at what is known about the possibilities of mitigation. The release of the different working groups’ reports is staggered over a year, and the August 2021 report is Working Group I’s report on the physical science.
• Summary for policymakers: This document has a summary for policymakers, and after the five-day plenary process which ended on August 6th 2021, the governments (a part of the IPCC) also worked through a draft summary prepared by the scientific authors to produce a text on which all could agree. Now everyone will meet at the COP26, the UN climate conference which will take place in Glasgow in November 2021.
• Clear learnings: This report presents the threat more clearly than the IPCC’s previous major assessment, AR5, published in 2013-14. 

1. The Earth has warmed over a tenth of a degree since then; it is now approximately 1.1ºC (2ºF) hotter than it was in the second half of the 19th century. 
2. Even if the countries of the world cut their greenhouse-gas emissions dramatically (they are not yet on a consistent downward trend of any sort) the IPCC finds that temperatures are very likely to be 1.5ºC higher than they were in the 19th century by 2050.
3. That breaks the more ambitious of the goals for limiting climate change that the world signed up to in the Paris agreement of 2015.
4. Greenhouse-gas emissions have produced a planet more than 1°C (1.8°F) warmer than it was in pre-industrial days. The atmosphere is now producing heavy weather in ways both predicted and surprising. 
5. Sadly, this is when 2021 will probably be one of the 21st century’s coolest years. 
6. If temperatures rise by 3°C above pre-industrial levels in the coming decades, large parts of the tropics risk becoming too hot for outdoor work. 
7. Coral reefs and the livelihoods that depend on them will vanish and the Amazon rainforest will become a ghost of itself. Severe harvest failures will be commonplace. Ice sheets in Antarctica and Greenland will shrink past the point of no return, promising sea rises measured not in millimetres, as today’s are, but in metres.

• Paris promise 2015: Six years ago, in Paris, the countries of the world committed themselves to avoiding the worst of that nightmare by eliminating net greenhouse-gas emissions quickly enough to hold the temperature rise below 2°C. Their progress towards that end remains bad. Even now if more efforts are made to meet the 2°C goal, it would not stop forests from burning today; prairies would still dry out tomorrow, rivers break their banks and mountain glaciers disappear.
• Carbon budget: IPCC had explained earlier that the Earth's warming depends closely on "cumulative greenhouse-gas emissions", and “carbon budget” associated with various temperatures may be calculated. 

1. For latest AR6 this was done, and the budget associated with a 50:50 chance of staying below 1.5ºC allows just 500 bn more tonnes of carbon dioxide to be emitted. 
2. That is about 15 years of industrial emissions at current rates (emissions from deforestation make things worse). 
3. For that to happen, the whole world has to be at net-zero before 2050.

• What kind of change is arriving: The report’s 234 authors base these conclusions on “multiple lines of evidence”: not just the output of computer models but also on an improved physical understanding of various physical processes involved. The authors stress that such changes are now “affecting every inhabited region across the globe, with human influence contributing to many observed changes in weather and climate extremes”.
• Technical: An important prediction is the report’s estimate of the “equilibrium climate sensitivity” — the amount of warming to be expected as a result of a doubling of the carbon-dioxide level. 

1. In 2007’s AR4, this number was put between 2 and 4.5ºC; in 2013’s AR5 the uncertainty had increased slightly, expanding the range to 1.5-4.5ºC (range 3). 
2. Now in 2021, it has been halved: AR6 puts the sensitivity at 2.5-4ºC, with a best estimate of 3ºC.
3. The report stresses that the world is now living through climate change, not watching it draw near.

• Ray of hope: The report finds that large-scale carbon-dioxide removal from the atmosphere might indeed be a way of reducing temperatures. The truth is that though everyone's talking of long-term cuts, in near term everyone is actually depending on such removals to achieve their commitments. But humanity must remember that such removals will impact things that go beyond temperature, including food production, biodiversity and water availability and quality.
• Methane: It is the second most important of the greenhouse gases being emitted in bulk by humankind. The atmospheric methane level, like the atmospheric carbon-dioxide level, is now higher than ever. But unlike carbon dioxide, atmospheric methane is short-lived and cuts in methane emissions pay off much faster than cuts in carbon dioxide. If the world is serious about trying to keep below 2ºC of warming, cutting methane emissions (both from industry and agriculture) must be a priority. 
• Sulphates: This is also needed because of the effects of another pollutant—  sulphates, given off mostly by coal plants and by heavy fuel oils. Unlike greenhouse gases, sulphates reduce warming by reflecting incoming sunlight back out into space. The IPCC estimates that in doing so they probably keep the world about 0.5ºC cooler than it would otherwise be; if it were not for sulphates, the world would have a 50/50 chance of being 1.5ºC or more warmer than the 19th century already. So sulphates are good, right? No. 

1. Over past decades they have contributed a lot to the particulate air pollution that has killed tens of millions. 
2. As a result they have increasingly been scrubbed out of fuels and smoke stacks. 
3. The IPCC report finds that continuing this good work on air pollution contributes to net warming in all the emission scenarios it studied. 
4. Hence promoting rapid and sustained cuts in methane emissions is needed. Why? Because without increased cuts in methane, improving air quality adds to the challenge of rising temperatures.

• No place to hide: In 2021, it became clear that there was no safe place to hide, when climate change-induced disaster strike. The ground under the German town of Erftstadt is torn apart like tissue paper by flood waters; Lytton in British Columbia is burned from the map just a day after setting a freakishly high temperature record; cars float like dead fish through the streets-turned-canals in the Chinese city of Zhengzhou. 

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