Five things we learnt from the IPCC’s latest global climate report
The UN’s Intergovernmental Panel on Climate Change’s (IPCC) sixth assessment report on the state of the planet’s climate makes for sobering reading, but it’s not all bad news.
Formed in 1988, the IPCC is a body made up of the world’s leading climate scientists with members from 195 countries. Back in 1990 it issued its first report warning of the potential dangers of rising greenhouse gas emissions. Here are the key points from its latest report.
Human activity over the last 100 years is to blame for significant increases in temperature
The report confirms that human activities have changed our climate and led to a significant increase in heatwaves, floods, droughts and wildfire. The researchers estimate that emissions of greenhouse gases from human activities are responsible for raising global surface temperatures by around 1.1°C since 1850-1900, with the last five years being the hottest on record.
If this trend is allowed to continue, global temperature is expected to reach or exceed the limit of 1.5°C of warming laid out in the Paris Agreement within the next 20 years, the researchers say.
“This report is a reality check,” said IPCC Working Group Co-Chair Valérie Masson-Delmotte. “We now have a much clearer picture of the past, present and future climate, which is essential for understanding where we are headed, what can be done, and how we can prepare."
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It’s affecting every region on Earth
Many characteristics of climate change directly depend on the level of global warming, but what people experience locally is often very different to the global average. For example, warming over land is larger than the global average, and it is more than twice the average in the Arctic.
The report projects that in the coming decades changes on climate will increase in every region on Earth. If global warming is kept to 1.5°C, we will still see an increase in heat waves, and longer warm seasons and shorter cold seasons. But if that figure reaches 2°C, heat extremes would more often reach the critical thresholds where they can cause serious issues for agriculture and health, the report shows.
“Climate change is already affecting every region on Earth, in multiple ways. The changes we experience will increase with additional warming,” said IPCC Working Group Co-Chair Panmao Zhai.
It’s about more than rising temperatures
Though the focus tends to be on rising temperatures, climate change is also having a significant effect on the global patterns of rain, wind and snow. Changes in the climate are affecting the water cycle, bringing more intense rainfall and flooding, as well as more severe periods of drought in many regions.
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Rainfall is likely to increase in high latitudes, and decrease over large areas of the subtropics. Local changes are also likely to occur to monsoon seasons.
Rising temperatures will also accelerate the loss of seasonal snow cover, the melting of glaciers and ices sheets, and the loss of summer Arctic sea ice, the report states.
“The report finds strengthened evidence that human-caused warming of climate is intensifying the global water cycle, including its variability and the severity of very wet and very dry weather and climate events affecting all regions,” said report author Prof Richard Allan, Professor of Climate Science at the University of Reading.
“The newly assessed science is clear that without rapid and sustained cuts in human-caused greenhouse gas emissions, water cycle extremes will continue to intensify with future increases in global surface temperature, along with more severe associated flooding and drought events.
Extreme sea level events that previously occurred once in 100 years could happen every year by the end of this century, the report states.
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Current measures are not enough
The report provides new estimates of the chances of crossing the global warming level of 1.5°C in the next decades, and finds that unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting warming to close to 1.5°C or even 2°C will be beyond reach.
“If there was still a need for a proof that climate change is caused by human activities this is the report that provides it. The report goes well beyond the previous IPCC assessment of 2013 and resolves all major uncertainties, to provide the clearest picture yet of the effect of human activities on the climate and on weather extremes,” said report author Prof Corinne Le Quéré, Royal Society Professor of Climate Change Science at the University of East Anglia.
“The message could not be clearer, as long as we continue to emit CO2 the climate will continue to warm and the weather extremes – which we now see with our own eyes – will continue to intensify. Thankfully we know what to do: stop emitting CO2.”
There’s still time to act
It’s not all bad news. Significant and sustained reductions in the emissions of carbon dioxide and other greenhouse gases over the coming decades years could limit climate change and even see global temperatures stabilise, the report states.“Every small increase in warming leads to greater impacts.
We are already seeing the consequence of human impacts on the climate with near global increases in heat and rainfall extremes, which have had severe impacts in many parts of the world, including Australia,” said Associate Professor Shayne McGregor, from the School of Earth, Atmosphere and Environment at Monash University.
“The next two decades are particularly critical. It will require sustained and concerted global efforts targeting rapid reductions in CO2, methane and other greenhouse gases to limit warming to 1.5°C in line with the Paris Agreement.”
Jason is the commissioning editor for BBC Science Focus. He holds an MSc in physics and was named Section Editor of the Year by the British Society of Magazine Editors in 2019. He has been reporting on science and technology for more than a decade. During this time, he's walked the tunnels of the Large Hadron Collider, watched Stephen Hawking deliver his Reith Lecture on Black Holes and reported on everything from simulation universes to dancing cockatoos. He looks after the magazine’s and website’s news sections and makes regular appearances on the Instant Genius Podcast.
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