Professor Richard Betts MBE, of the Met Office and the University of Exeter, says the Working Group II report demonstrates the “vast body of evidence” that humans are causing climate change with damaging impacts worldwide.
Approved by 195 IPCC member governments, the report calls climate change a threat to human wellbeing and the health of the planet, and says taking action now can secure our future.
It also says people and ecosystems least able to cope are being hardest hit.
Professor Betts, part of Exeter’s Global Systems Institute, said: “This report shows that climate change is already having widespread impacts, and further impacts are in the pipeline even if emissions are cut as rapidly as the most ambitious scenario suggests.
“We also conclude that many future climate-related risks are more severe than previous IPCC assessments.
“We urgently need to adapt to these changes to manage these unavoidable risks, as well as urgently stopping our carbon emissions from burning fossil fuels and deforestation in order to stop these risks from increasing further.”
IPCC Chair Hoesung Lee said: “This report is a dire warning about the consequences of inaction.
“It shows that climate change is a grave and mounting threat to our wellbeing and a healthy planet. Our actions today will shape how people adapt and nature responds to increasing climate risks.”
The report – which draws on research including a variety of work by the University of Exeter – says the world faces unavoidable multiple climate hazards over the next two decades with global warming on track to exceed 1.5°C (2.7°F) above pre-industrial levels.
Even temporarily exceeding this warming level will result in additional severe impacts, some of which will be irreversible.
Risks for society will increase, including to infrastructure and low-lying coastal settlements.
Increased heatwaves, droughts and floods are already exceeding plants’ and animals’ tolerance thresholds, driving mass mortalities in species such as trees and corals.
These weather extremes are occurring simultaneously, causing cascading impacts that are increasingly difficult to manage.
However, the report does show that many of the risks can be reduced by adaptation, as long as further global warming is limited to low levels.
To avoid mounting loss of life, biodiversity and infrastructure, ambitious, accelerated action is required to adapt to climate change, at the same time as making rapid, deep cuts in greenhouse gas emissions.
The new report is the second instalment (Working Group II) of its Sixth Assessment Report (AR6) which aims to assess risks arising from climate change.
The third instalment (Working Group III) focusses on mitigation – the measures needed to reduce greenhouse gas emissions to limit further climate change – and is scheduled for publication in April.
Professor Catherine Mitchell is a Coordinating Lead Author in Chapter 13: National and Sub-national Policies and Institutions; and Professor Patrick Devine-Wright is a Lead Author in Chapter five: Demand, services and social aspects of climate mitigation.