Increasing temperatures will lead to more intense rainfall and flooding, as well as more agricultural and ecological droughts
THE frequency and intensity of extreme weather events associated with human-caused climate change is going to get worse as the world reaches 1.5°C of warming in the next 20 years, according to the latest report from the Intergovernmental Panel on Climate Change (IPCC). However, it says there is still time to limit the damage.
The IPCC last reported on the science of climate change in its fifth assessment report in 2013. The new publication (https://bit.ly/2VXsPEv) is the first part of the IPCC’s sixth assessment report, with two other reports also in development.
The report is written by 234 scientists from 66 countries, along with 517 contributing authors, who have brought together the findings from more than 14,000 peer-reviewed studies. They used improved observational datasets to assess historical warming along with the latest advancements in climate science to conclude that “it is unequivocal that the increase of CO2, methane, and nitrous oxide in the atmosphere over the industrial era is the result of human activities and that human influence is the principal driver of many changes observed across the atmosphere, ocean, cryosphere and biosphere.” The report has been approved by 195 governments.
The aim of the Paris Agreement is to limit warming to 1.5°C above pre-industrial times, but we have already reached 1.1°C. Since 1850, humanity has been responsible for pumping 2,400bn t of CO2 into the atmosphere, and atmospheric CO2 concentrations are now higher than at any time in the last 2m years. To have a chance of keeping to the 1.5°C target, there is therefore a limit – a “carbon budget” on how many more tonnes of CO2 can be emitted before the target is breached. For an 83% chance of staying within 1.5°C, only another 300bn t can be emitted. If 900bn t are emitted, the chances of staying on track drop to 17%.
The report models a number of scenarios depending on levels of emissions, their associated temperature rises, and the consequences of each.
Under all scenarios – even if emissions are kept low – global temperatures will reach 1.5°C within the next 20 years. Towards the end of the century – between 2081–2100 – temperatures are “very likely to be higher by 1.0°C to 1.8°C under the very low GHG emissions scenario considered, by 2.1°C to 3.5°C in the intermediate scenario, and by 3.3°C to 5.7°C under the very high GHG emissions scenario.”
However, there is still a window of opportunity to stop temperatures rising further than 1.5°C if large-scale action is undertaken immediately. Under the best-case scenario of low emissions, warming will reach 1.5°C by 2040, rise to 1.6°C by 2060, but then cool back to 1.4°C by 2100.
This article is adapted from an earlier online version.
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