The Intergovernmental Panel on Climate Change
has warned the
effect of unchecked global warming could be "severe, pervasive and
To get an idea of how global temperatures could evolve
in the next 85 years, the IPCC looks at a range of scenarios, or
pathways. In all but the IPCC's most stringent mitigation pathway,
the world looks on course for dangerous levels of warming.
So how did climate skeptic campaigner, Matt Ridley,
come to the opposite conclusion in an
article last week? He argues that even the IPCC's most
severe scenario doesn't suggest dangerous levels of warming. We
take a look at the IPCC's pathways to understand how it projects
future warming - and where Ridley went wrong.
The IPCC looks at a wide range of potential futures
based on how big or small countries' collective greenhouse gas
emissions are. To examine these, it developed a range of emissions
pathways - each known as Representative Concentration Pathways
Ridley describes the IPCC's
four pathways in his recent article, and claims none of
them imply dangerous levels of warming. He begins:
"Three of the models show moderate, slow and mild
warming, the hottest of which leaves the planet just two degrees
Centigrade warmer than today in 2081-2100. The coolest comes out
just 0.8 degrees warmer."
Ridley's talking about the IPCC's three lowest
scenarios - leaving out the one where emissions continue unchecked
for now. But he seems to have got the numbers wrong.