Alister Doyle Oslo

Global warming will disrupt food supplies, slow economic growth and may already be causing irreversible damage to nature, according to a UN report due this week that will put pressure on governments to act.

A 29-page draft by the Intergovernmental Panel on Climate Change (IPCC) will outline ways to adapt to rising temperatures, more heatwaves, floods and rising seas.

“The scientific reasoning for reducing emissions and adapting to climate change is becoming more compelling,” said Rajendra Pachauri, the chair of the IPCC, in Beijing.

Scientists and more than 100 governments will meet in Japan from tomorrow until Saturday to edit and approve the report. It will guide policies in the run-up to a UN summit in Paris in 2015 to decide a deal to curb rising greenhouse gas emissions.

The draft projects risks such as food and water shortages and extinctions of animals and plants. Crop yields will range from unchanged to a fall of up to 2 percent a decade, compared with a world without warming, it says. And some natural systems may face risks of “abrupt or drastic changes” that could mean irreversible shifts, such as a runaway melt of Greenland or a drying of the Amazon rainforest.

It says there are “early warning signs that both coral reef and Arctic systems are already experiencing irreversible regime shifts”. Corals are at risk in warmer seas and the Arctic region is thawing fast.

Climate change will hit growth. Warming of 2.5ºCelsius above pre-industrial levels could mean “global aggregate economic losses between 0.2 percent and 2.0 percent of income”, it says.

Almost 200 governments have agreed to limit warming to less than 2ºC above pre-industrial times, mainly by curbing emissions from burning fossil fuels. Temperatures have already risen by about 0.8ºC.

“A range of impacts from climate change are happening,” said Chris Field of Stanford University and a co-chair of the report. “Risks are much greater with more warming than less warming. And it doesn’t require 100 percent certainty before you have creative options for moving forwards… there are compelling adaptation options.”

The report points to options like improved planning for disasters such as hurricanes or flooding, efforts to breed drought or flood-resistant crops, measures to save water and energy or wider use of insurance.

Field said the IPCC would have to take account of thousands of comments since the draft was leaked to a climate sceptic’s website late last year.

And the findings will be under scrutiny after the previous assessment in 2007 wrongly projected that Himalayan glaciers might all melt by 2035, affecting water supplies for millions of people from China to India. This time, a sub-chapter projects the ice will range from a 2 percent gain to a 29 percent loss by 2035. “It is virtually certain that these projections are more reliable than an earlier erroneous assessment,” it says.

The study is the second part of a three-part report. A third, due in Berlin in mid-April, will show solutions. – Reuters