Paris Will Reduce Temperatures By Only 0.17C–Lomborg

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By Paul Homewood

Various claims have been made about the effect that the Paris Agreement would have on emissions and global temperatures.

The most authoritative analysis came from Bjorn Lomborg in November 2015, just before the Paris Agreement was signed:

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Lomborg’s paper, it should be noted, was fully peer reviewed and published the Global Policy journal.

Lomborg’s blog summarised his findings:

Paris climate promises will reduce temperatures by just 0.05°C in 2100 (Press release)

A new peer-reviewed paper by Dr. Bjorn Lomborg published in the Global Policy journal measures the actual impact of all significant climate promises made ahead of the Paris climate summit.

Governments have publicly outlined their post-2020 climate commitments in the build-up to the December’s meeting. These promises are known as “Intended Nationally Determined Contributions” (INDCs).

Dr. Lomborg’s research reveals:

The climate impact of all Paris INDC promises is minuscule: if we measure the impact of every nation fulfilling every promise by 2030, the total temperature reduction will be 0.048°C (0.086°F) by 2100.
Even if we assume that these promises would be extended for another 70 years, there is still little impact: if every nation fulfills every promise by 2030, and continues to fulfill these promises faithfully until the end of the century, and there is no ‘CO₂ leakage’ to non-committed nations, the entirety of the Paris promises will reduce temperature rises by just 0.17°C (0.306°F) by 2100.
US climate policies, in the most optimistic circumstances, fully achieved and adhered to throughout the century, will reduce global temperatures by 0.031°C (0.057°F) by 2100.
EU climate policies, in the most optimistic circumstances, fully achieved and adhered to throughout the century, will reduce global temperatures by 0.053°C (0.096°F) by 2100.
China climate policies, in the most optimistic circumstances, fully achieved and adhered to throughout the century, will reduce global temperatures by 0.048°C (0.086°F) by 2100.
The rest of the world’s climate policies, in the most optimistic circumstances, fully achieved and adhered to throughout the century, will reduce global temperatures by 0.036°C (0.064°F) by 2100.

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Before anybody questions whether GHGs have any effect on temperature, Lomborg points out that he uses the IPCC climate models, so as to ensure consistency:

The peer-reviewed paper takes the greenhouse gas emission reduction commitments (INDCs) and runs a climate model with and without them. The paper uses the MAGICC climate model, which has been used across all five IPCC reports and was co-funded by the US EPA. It is run with standard parameters. Sensitivity analysis shows that different assumptions of climate sensitivity, carbon cycle model or scenario do not substantially change the outcome.

The paper uses the same basic methodology of Tom Wigley, who analyzed the Kyoto Protocol in a much-cited paper in 1998.

Christina Figueres

He also deals with claims put forward by Christina Figueres, which suggest a much bigger effect from Paris:

“You describe a 0.05°C reduction, but the UN Climate Chief, Christina Figueres, said Paris could lead to a 2.7°C rise instead of 4°C or 5°C. Why?”

Christiana Figueres quote: “The INDCs have the capability of limiting the forecast temperature rise to around 2.7 degrees Celsius by 2100, by no means enough but a lot lower than the estimated four, five, or more degrees of warming projected by many prior to the INDCs.”

Dr. Lomborg said: “That entirely misrepresents the world’s options. The 2.7°C comes from the International Energy Agency and essentially assumes that if governments do little in Paris and then right after 2030 embark on incredibly ambitious climate reductions, we could get to 2.7°C.

That way of thinking is similar to telling the deeply indebted Greeks that just making the first repayment on their most pressing loans will put them on an easy pathway to becoming debt-free. It completely misses the point.

Figueres’ own organization estimates the Paris promises will reduce emissions by 33Gt CO₂ in total. To limit rises to 2.7°C, about 3,000Gt CO₂ would need to be reduced – or about 100 times more than the Paris commitments (see figure below). That is not optimism; it is wishful thinking.

Bob Ward

Finally, he meets head on a criticism from Bob Ward on his paper:

Response to Bob Ward

Activism Dressed Up as Science

Bob Ward of the Grantham Institute on Climate Change at the LSE is aggressively promoting a short text that he claims to document a “fundamental methodological flaw” in my research paper, “Impact of Current Climate Proposals”.

In a press release, a letter to the Financial Times, and on social media, Ward suggests that his musings justify the withdrawal of my peer-reviewed research paper.

Communications professional Ward has every right to posit his personal view on how climate impact should be measured, even if in doing so he demonstrates a misunderstanding of methodology, modeling and my paper.

However, Ward is going much further than that. He is trying to smear my research, the journal that published it, and revoke my right to publish, simply because he thinks I should have approached the paper differently.

That is deeply troubling for any researcher, regardless of his or her personal beliefs.

Lomborg’s full response to Ward is here, and fully exposes just how limited the latter’s understanding of the science is (or how dishonest he is).

As Lomborg sums up:

Ward, who has an undergraduate degree in geology and an unfinished PhD thesis on paleopiezometry, appears to have read my article only cursorily, and to misunderstand the approach. He certainly drastically misrepresents it. Understanding a research paper, in my opinion, should be a first step before calling for its withdrawal.

Ward’s response to my paper is just three pages long, but contains five serious examples where he apparently misunderstands or misses fundamental points.

Ward questions why the journal Global Policy published my paper and ‘how it passed peer review’. The more salient question is how he produced – and is publishing – a response that so fundamentally misunderstands the paper it responds to.