“The next two decades are particularly critical”
Human activity over the last 100 years is to blame for increases in temperature
Human activities have changed the climate and led to a significant increase in heatwaves, floods, droughts and wildfire. The researchers estimate that emissions of greenhouse gases from our 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 is allowed to continue, then global temperature is expected to reach or exceed the limit of 1.5°C of warming laid out in the Paris Agreement (a legally binding international treaty on climate change) within the next 20 years.
“This report is a reality check,” said IPCC Working Group co-chair Dr 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.”
Climate change is affecting every region
If global warming is kept to 1.5°C, we will still see an increase in heat waves, along with longer warm seasons and shorter cold seasons. But if that figure reaches 2°C, heat extremes would more often reach critical thresholds where they can cause serious issues for agriculture and health.
“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 increasing temperatures, climate change is having a significant impact on global patterns of rain, wind and snow, bringing more intense rainfall and flooding, as well as severe periods of drought.
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 accelerate the loss of seasonal snow cover, the melting of glaciers and ice 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, from the University of Reading.
Extreme sea level events that previously occurred once in 100 years could happen every year by the end of this century, the report states.
Current measures are not enough
The report finds that unless there are immediate, 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 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, from 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 emissions over the coming decades could limit climate change and even see global temperatures stabilise.
“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,” said author Shayne McGregor, an associate professor from Monash University.