Climate scientists say human influence makes more ‘polar jet stream’ events and downpours likely as climate change progresses
Record-breaking heat, intense rainfall and extreme storms will be frequent and likely across large parts of the globe as climate change progresses, the UN said on Friday.
The assessment by the Intergovernmental Panel on Climate Change (IPCC) of ongoing science and projections is largely in line with what many academics and energy companies have been saying for some time.
“On present trends, the impacts of climate change will accelerate as the climate system takes further environmental and economic changes beyond natural variability,” it warned.
“The impacts are likely to be large enough to affect at least half of all potentially impacted areas and human decision-making will have to change.”
The report said it would be “possible to attribute impacts of climate change to human influence on the climate system”, although the degree of certainty was unclear.
The team led by the Swiss government noted for instance that the past five years have been the hottest on record with an “extensive record of long-term trends” made up of more than 5,000 datasets.
Last year was the fourth hottest on record, with 2015, 2014 and 2010 also setting records.
Climate scientists say the phenomenon of human caused climate change is undeniable. But questions linger over how confident the IPCC is that humans will be largely to blame by the end of the century, with uncertainty remaining on the precise contributions from natural variation.
The UN’s climate change body in October last year said rising carbon dioxide emissions from burning fossil fuels and deforestation were responsible for man-made global warming, with a “high confidence”.
A year earlier, they added that it was “very likely”, or 97% of expert analyses, that human activity was the main cause of global warming.
The IPCC, however, in November last year substantially downgraded its position on global warming, to stating only that average temperatures were likely to increase by 2C (3.6F) by the end of the century, rather than the stated “very likely” of a decade earlier.
While the new report has “high confidence” in some projections, such as on the impacts of global warming, there are parts which remain in doubt.
“There is continued uncertainty over some projections regarding sea level rise, in particular the rate and geographic scale of climate change,” the UN scientists wrote.
They predicted that up to 65% of non-latitudinal coastal areas were at risk of flooding from 2C and 2.5C of global warming, and up to 37% of locations could be faced with water shortages by the end of the century.
Among regions most at risk of violent climate change impacts are sub-Saharan Africa, south-east Asia, the Middle East and the Pacific. In Europe, from the UK to Switzerland, there is rising concern over the impact of the Mediterranean drought, which has been called the worst in over 1,000 years, and heatwaves in Northern Europe.
Several countries have expressed alarm over the rise in the sea level. Sweden has said it will almost double military spending to protect coastal cities.
Asked whether the IPCC report showed the change could be exponential, Don Watson, a professor at the Australian National University, said: “It’s always hard to give a general view of future events because we just don’t know enough.
“The way our climate system works is that it is an incredibly complex environment, and all sorts of unpredictable things can and do happen. This report is a holistic assessment of all the latest information which goes back decades. All those uncertainties have to be weighed against the probability they add up to, which is very low.”
He said the report provided plenty of cause for concern but did not specify how many degrees the planet was likely to warm by 2100.
“If this IPCC report has 100% certainty, that would mean that there is a total global meltdown by 2100,” he said. “Well, we’ve seen melt earlier than that.
“Heatwaves happen in the Arctic, but they happen all over the world. This report doesn’t say we’re going to have 100% temperatures increase by 2100, but nor does it say we aren’t. It is obviously going to be much more likely and there’s no way to ensure that either.”