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Carbon Brief Staff

07.04.2011 | 4:00pm
ScienceMatt Ridley’s climate science based on weak foundations
SCIENCE | April 7. 2011. 16:00
Matt Ridley’s climate science based on weak foundations

Popular science writer Matt Ridley had a piece in Tuesday’s edition of the Times which likens climate change to a nosebleed – and the proposed solutions to a tourniquet round your neck. Ridley writes:

“if you are bleeding to death from a severed limb, then a tourniquet may save your life, but if you have a nosebleed, then a tourniquet round your neck will do more harm than goodâ?¦”

So what is the basis for Ridley’s argument?

With regard to the impacts of climate change, he makes three key arguments – that sea level rise is a ‘slight nosebleed’, (i.e. insignificant), that the impacts of ‘most of the other symptoms of climate change’ are also slight, and that the rate of temperature increase is ‘not on track to do net harmâ?¦ by the end of this century.’

To support his first point, Ridley cites a paper in the Journal of Coastal Research in November 2010, recently published online and profiled last week on prominent climate sceptic website Watts Up With That.

The paper looked at tide gauges in North America to ascertain whether sea-level is rising in the USA. It concluded that although sea level rise is still occurring, it is occurring more slowly than expected, and the rise is slowing down rather than speeding up. The first part of the abstract states:

“Without sea-level acceleration, the 20th-century sea-level trend of 1.7 mm/y would produce a rise of only approximately 0.15 m from 2010 to 2100”

Ridley argues that:

“Sea level rise is the greatest potential threat to civilisation posed by climate change because so many of us live near the coast. Yet, at a foot a century and slowing, it is a slight nosebleed.”

In his article, Ridley does not however consider any other research in this area. Other research on this subject disagrees with its conclusion – a fact illustrated by comments made by oceanographer and climate scientist John Church. Church,  who is writing the chapter on sea level rise for the IPCC’s 2013 update, told Australia’s biannual climate science conference just earlier this week that sea levels are rising at the upper end of projections by the IPCC – meaning a rise of 60-80cm by 2100.

A review of the subject published in January 2010 concluded that:

“Most recent developments indicate that sea level is currently rising, slightly faster since the early 1990s than during the previous decades.”

Why is there disagreement within the scientific literature? It could be for a variety of reasons – including contradictions between tide gauge data and the satellite data which is also used to measure sea levels, the impact on tide gauge data of land subsidence, and the fact that sea level rise varies regionally.

Another uncertainty arises from the impact of melting ice sheets – a factor which the IPCC is known to have underestimated in its 2007 report. Research published earlier this year suggested ice sheet loss has accelerated over the last 18 years, and that if this trend continues ice sheets will be the dominant contributor to sea level rise in the 21st century. At the upper end of the scale, some scientists suggest that this could lead to a sea level rise of up to 1.9 metres by 2100 (relative to 1990 levels).  

The conclusions of the research Ridley cites are interesting. They need to be tested against the rest of the scientific literature as this is a complex area. It is also an area where the risks in terms of impacts on human population are very significant. Bearing this in mind, it would seem unwise to draw such definitive conclusions from just one paper.

Ridley moves from this assessment of sea level rise to apply the ‘slight nosebleed’ comparison to

“most of the other symptoms of climate change, such as Arctic sea ice retreat, in terms of their impact.”

No supporting scientific literature is given for this statement, which is at odds with the views of the scientific community, to put it mildly.

To briefly consider Arctic sea ice – loss of the ice leads to further regional warming, as with the very reflective ice gone, less of the sun’s energy is reflected back into space.

A major gathering of top climate scientists, who came together to review the scientific data on climate change in March 2009 in the run-up to the Copenhagen summit, concluded that

“Recent observations show that greenhouse gas emissions and many aspects of the climate are changing near the upper boundary of the IPCC range of projections. Many key climate indicators are already moving beyond the patterns of natural variability within which contemporary society and economy have developed and thrived. These indicators include global mean surface temperature, sea-level rise, global ocean temperature, Arctic sea ice extent, ocean acidification, and extreme climatic events. With unabated emissions, many trends in climate will likely accelerate”

Ridley’s article continues:

“The rate of increase of temperature (0.6C [sic] in 50 years) is not on track to do net harm (which most experts say is 2C [sic]) by the end of this century.”

This statement is problematic, because it makes the assumption that as temperatures rise, they will continue to do so at a stable rate.

Again, Ridley is at odds with the scientific understanding of climate. The IPCC’s projections suggest that temperature will rise by 2°C (relative to pre-industrial values) by the end of the 21st century, even under the most moderate emissions scenarios, which we are currently exceeding. Under the highest emissions scenarios, a temperature increase of 4°C is more likely.

Ridley’s suggestion that the temperature increase will not do “net harm” contrasts with the conclusions of the IPCC – which concludes for example that the health impacts of climate change will be ” overwhelmingly negative” and that ” the resilience of many ecosystems is likely to be exceeded”.

Ridley’s article is about the potential impacts of climate change, and what we as a society should be doing to avoid those impacts. Interesting as his argument is (also citing a paper on the impact of biofuels), it is built on weak foundations. One paper on sea level rise has not overturned the weight of evidence, and of scientific opinion, on climate change.

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