Human-induced climate change is already affecting many weather and climate extremes in every region across the globe. Scientists are also observing changes across the whole of Earth’s climate system; in the atmosphere, in the oceans, ice floes, and on land.
change is intensifying at a rapid rate, yet some trends are now
irreversible, at least during the present time frame, according to the
latest Intergovernmental Panel on Climate Change (IPCC)
report, released on Monday.
It shows that human-induced
climate change is already affecting many weather and climate extremes in every region across the globe. Scientists are also observing changes in the atmosphere, in the oceans, ice floes, and on land, many of which are unprecedented, and some already ‘irreversible’ for centuries.
The report, prepared by 234 scientists from 66 countries,
highlights that human influence has warmed the climate at a rate that is unprecedented in at least the last 2,000 years. In 2019, atmospheric carbon concentrations were higher than at any time in at least 2 million years, and concentrations of methane and nitrous oxide were higher than at any time in the last 800,000 years.
The global surface temperature has increased faster since 1970
than in any other 50-year period over a least the last 2,000 years.
For example, temperatures during the most recent decade (2011–2020)
exceed those of the most recent multi-century warm period, around 6,500
years ago, the report indicates.
The document shows that emissions of greenhouse gases from human
activities are responsible for approximately 1.1°C of warming between
1850-1900, and finds that averaged over the next 20 years, global temperature is expected to reach or exceed 1.5°C of heating. The IPCC scientists warn global warming of 2°C will be exceeded during the 21st century.
The assessment is based on improved data on historical warming, as
well as progress in scientific understanding of the response of the
climate system to human-caused emissions. The scientists also point out that evidence of observed changes in
extremes such as heatwaves, heavy precipitation, droughts, and tropical
cyclones, and their attribution to human influence, has strengthened.
They add that many changes in the climate system become larger in direct
relation to increasing global warming.
“It has been clear for decades that the Earth’s climate is
and the role of human influence on the climate system is undisputed,”
said IPCC Working Group I Co-Chair, Valérie Masson-Delmotte. “Yet
the new report also reflects major advances in the science of attribution –
understanding the role of climate change in intensifying specific
weather and climate events”.
But there is still time to limit climate change, IPCC
experts say. Strong and sustained reductions in emissions of carbon dioxide (CO2) and other greenhouse gases, could quickly make air quality better, and in 20 to 30 years global temperatures could stabilize.
The report makes clear that while natural drivers will modulate
human-caused changes, especially at regional levels and in the near
the term, they will have little effect on long-term global warming.
The IPCC experts project that in the coming decade's climate changes will increase in all regions. For 1.5°C of global warming, there will be increasing heat waves, longer warm seasons and shorter cold seasons. At 2°C of global warming, heat extremes are more likely to reach critical tolerance thresholds for agriculture and health.
But it won’t be just about temperature. For example, climate change is intensifying the natural production of water – the water cycle. This brings more intense rainfall and associated flooding, as well as more intense drought in many regions.
It is also affecting rainfall patterns. In high latitudes,
precipitation is likely to increase, while it is projected to decrease over large parts of the subtropics. Changes to monsoon rain patterns are expected, which will vary by region, the report warns. The report also indicates that further warming will amplify permafrost thawing, and the loss of seasonal snow cover, melting of glaciers and ice sheets, and loss of summer Arctic sea ice.
Changes to the ocean, including warming, more frequent marine
heatwaves, ocean acidification, and reduced oxygen levels affect both
ocean ecosystems and the people that rely on them, and they will
continue throughout at least the rest of this century.