The world’s leading climate scientists have warned there is only a dozen years 
for global warming to be kept to a maximum of 1.5C, beyond which even half a 
degree will significantly worsen the risks of drought, floods, extreme heat and 
poverty for hundreds of millions of people.

 The authors of the landmark report by the UN Intergovernmental Panel on 
Climate Change (IPCC) released on Monday say urgent and unprecedented changes 
are needed to reach the target, which they say is affordable and feasible 
although it lies at the most ambitious end of the Paris agreement pledge to 
keep temperatures between 1.5C and 2C.

 “It’s a line in the sand and what it says to our species is that this is the 
moment and we must act now,” said Debra Roberts, a co-chair of the working 
group on impacts. “This is the largest clarion bell from the science community 
and I hope it mobilises people and dents the mood of complacency.”


 At 1.5C the proportion of the global population exposed to water stress could 
be 50% lower than at 2C, it notes. Food scarcity would be less of a problem and 
hundreds of millions fewer people, particularly in poor countries, would be at 
risk of climate-related poverty.


 At 2C extremely hot days, such as those experienced in the northern hemisphere 
this summer, would become more severe and common, increasing heat-related 
deaths and causing more forest fires.


 But the greatest difference would be to nature. Insects, which are vital for 
pollination of crops, and plants are almost twice as likely to lose half their 
habitat at 2C compared with 1.5C. Corals would be 99% lost at the higher of the 
two temperatures, but more than 10% have a chance of surviving if the lower 
target is reached.


 “We have presented governments with pretty hard choices. We have pointed out 
the enormous benefits of keeping to 1.5C, and also the unprecedented shift in 
energy systems and transport that would be needed to achieve that,” said Jim 
Skea, a co-chair of the working group on mitigation. “We show it can be done 
within laws of physics and chemistry. Then the final tick box is political 
will. We cannot answer that. Only our audience can – and that is the 
governments that receive it.”


 He said the main finding of his group was the need for urgency. Although 
unexpectedly good progress has been made in the adoption of renewable energy, 
deforestation for agriculture was turning a natural carbon sink into a source 
of emissions. Carbon capture and storage projects, which are essential for 
reducing emissions in the concrete and waste disposal industries, have also 
ground to a halt.

 Reversing these trends is essential if the world has any chance of reaching 
1.5C without relying on the untried technology of solar radiation modification 
and other forms of geo-engineering, which could have negative consequences.

 Bob Ward, of the Grantham Research Institute on Climate Change, said the final 
document was “incredibly conservative” because it did not mention the likely 
rise in climate-driven refugees or the danger of tipping points that could push 
the world on to an irreversible path of extreme warming.


 At the current level of commitments, the world is on course for a disastrous 
3C of warming. The report authors are refuseing to accept defeat, believing the 
increasingly visible damage caused by climate change will shift opinion their 


 James Hansen, the former Nasa scientist who helped raised the alarm about 
climate change, said both 1.5C and 2C would take humanity into uncharted and 
dangerous territory because they were both well above the Holocene-era range in 
which human civilisation developed. But he said there was a huge difference 
between the two: “1.5C gives young people and the next generation a fighting 
chance of getting back to the Holocene or close to it. That is probably 
necessary if we want to keep shorelines where they are and preserve our coastal 


 “Climate change is occurring earlier and more rapidly than expected. Even at 
the current level of 1C warming, it is painful,” he told the Guardian. “This 
report is really important. It has a scientific robustness that shows 1.5C is 
not just a political concession. There is a growing recognition that 2C is 



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