Environment

‘Warning flag’: IPCC finds rapid land warming threatens food security

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Temperatures over the world's land areas are warming at about the twice the global rate, expanding deserts in Australia, Africa and Asia, and hitting food security hard, a new UN report finds.

The Intergovernmental Panel on Climate Change (IPCC) found that surface air temperatures between 2006 and 2015 were 1.53 degrees warmer than the pre-industrial average of 1850-1900.

That compared with the combined warming of land and oceans of 0.87 degrees, its special report on land said.

"Climate change, including increases in frequency and intensity of extremes, has adversely impacted food security and terrestrial ecosystems, as well as contributed to desertification and land degradation in many regions," the report's Summary for Policymakers said.

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The report, compiled by dozens of scientists and released in Geneva on Thursday, noted humans typically relied on land for their homes and the great bulk of their food, fibre and feed for animals.

Mark Howden, Director of the Climate Change Institute at the Australian National University and an IPCC Vice Chair, said the report was "a warning flag" about the threats and "how hard we need to go" to cut greenhouse gas emissions.

Land's effect on climate

About a quarter of the earth's ice-free land was already subject to human-caused degradation, with soil losses as much as 100 times higher than soil formation, the report said.

Australia, along with sub-Saharan Africa and parts of east and central Asia, was singled out as regions where rising evapotranspiration – caused by hotter temperatures and reduced rainfall – were causing deserts to expand.

Climate change would "ramp up" existing degradation, such as through erosion caused by more intense rainfall events, Professor Howden said.

But land would also affect the climate because land-clearing, methane from livestock, fertiliser, and other emissions related to farming and forestry are major sources of greenhouse gases.

"Just under a third of our emissions come from our food systems, globally," he said.

Temperatures are rising over land much faster than the global average with climate change. Australia is one nation where arid regions are expanding, the IPCC says in a new report.

Temperatures are rising over land much faster than the global average with climate change. Australia is one nation where arid regions are expanding, the IPCC says in a new report.Credit:Louise Kennerly

'Not safe at 2 degrees'

Andy Pitman, director of the ARC Centre of Excellence for Climate Extremes, said the thermal inertia of the oceans meant land warmed faster than the seas.

Where lands dry out, the cooling role of evaporation diminishes, so extreme temperatures are more intense.

"It's why the 2-degree ceiling agreed in Paris [at the climate summit in 2015] isn't safe," Professor Pitman said. "Two degrees in the global mean [translates to] very, very sizeable amounts of warming in heatwave conditions over land."

He cited farming regions such as Moree in northern NSW where last January's average temperatures "slaughtered" previous records, beating the norm by close to 4 degrees.

"We're seeing those extreme temperatures rapidly rising in part because in some regions we're seeing a drying," Professor Pitman said.

Australia has warmed about a degree in the past century, and the Bureau of Meteorology says day-time temperatures were both the hottest on record in the year to June and for the first seven months of this year.

Average soil moisture for 12 months to June 30 were also the lowest on record at just 8.5 per cent for the top metre. That beat the record low of 8.7 per cent 1914-15 and compared with an average of 12 per cent, the bureau said.

Rising temperatures and increase evaporation will affect crops and other food supplies, undermining food security, the IPCC said.

Rising temperatures and increase evaporation will affect crops and other food supplies, undermining food security, the IPCC said.Credit:DPA

The IPCC report said warming, changing precipitation patterns and the greater frequency of some extreme events "has already affected food security".

"Changes in climate can amplify environmentally induced migration both within countries and across borders," the report said, adding increaRead More – Source