10th August 2021
The assessment reports come in groups of three. This first report outlines the projected impacts of five emissions scenarios, which range from global net negative and net zero to emissions doubling by 2050 and 2100, compared to current levels.
The second and third reports, due to land in early 2022, will look at how to adapt to these impacts and how to prevent the worst-case scenarios.
Summarising the “physical science basis” for climate change, the report pulls together the findings from more than 14,000 peer-reviewed studies.
Here we take a look at the key messages from this landmark report.
“Global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades.”
The warming of the earth in recent decades has not been seen for millennia and is happening rapidly and affecting almost everywhere on the planet. According to the report, the global temperature increase from pre-industrial times is likely to breach 1.5°C – the Paris Agreement’s most ambitious pathway – by 2040. Temperatures have already risen by around 1.1C over the last century or so.
Under all emissions scenarios proposed in the IPCC report, the earth’s surface warming is projected to reach 1.5°C or 1.6°C in the next two decades.
For any chance of meeting the goal seen as essential to the survival of some vulnerable communities and ecosystems, drastic reductions in CO2 would be needed this decade and net zero emissions by 2050.
“Many changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets and global sea level.”
The report makes it very clear that we are getting closer to the point where changes to the climate are at irreversible tipping points. Ice-sheet collapse, massive forest loss or an abrupt change in ocean circulation cannot be ruled out, particularly in scenarios in which high emissions and significant warming occur towards the end of the century. For example, sea levels around the world are projected to increase by 2-3m over the next 2000 years and that is if warming can be kept to 1.5°C, it will be up to 6m at 2°C warming which would alter entire coastlines affecting hundreds of millions of people.
“It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.”
In its last report in 2013 (AR5), the IPCC concluded that human influence on climate system was “clear” however due to enormous developments in attribution science since then, this latest report has concluded there is “high confidence” that human activities are the main drivers of more frequent or intense heatwaves, glaciers melting, ocean warming and acidification.
“Climate change is already affecting every inhabited region across the globe with human influence contributing to many observed changes in weather and climate extremes.”
Modelling has shown that some mid-latitude and semi-arid regions, and the South American Monsoon region are projected to see the highest increase in temperature of the hottest days, at about 1.5-2 times the rate of global warming. The Arctic is projected to experience the highest increase in the temperature of the coldest days, at about 3 times the rate of global warming. And regions at high altitudes in the Northern Hemisphere are projected to warm by 2-4 times the level of global warming.
In a statement, the IPCC said it is hoping for policymakers and negotiators from all nations attending COP26 this November to fully understand the report and embed its implications into their choices. Critically, the report, for the first time, maps precisely how different global warming scenarios would affect different regions, nations and even cities. It also warns that no geographies will be immune to the physical impacts of climate change.
Recent UK action from the government, such as an ongoing consultation for greater ESOS reporting regulations, new rating systems for large buildings, TCFD and much more, are evidence of an ever increasing momentum towards better measurement, reporting and reduction of carbon emissions and increased planning for the future.
Climate change is no longer seen as a ‘future event’, it is happening now, with increasing extreme weather events including flooding, extreme heat and forest fires. The takeaway message is ‘plan for the future but also, prepare for the present’