Lomborg misses the turn

26th November 2015

A recent study by Bjorn Lomborg found that the combined Intended Nationally Determined Contributions (INDCs) Governments have submitted to the UNFCCC are only sufficient to reduce warming by 0.017 to 0.02°C by 2100.

The study massively underestimates the impact of INDCs on global emissions, and therefore warming, because it assumes emissions begin rising rapidly post-2030.

To estimate the impact of the Paris Agreement, an emission scenario including the INDCs must be compared with an emission scenario excluding the INDCs. INDCs are only defined until 2025/2030, so to estimate the temperature impact one needs to make assumptions on emissions after 2030. These emissions have a significant impact on temperatures in 2100.

The approach taken in the study by Bjorn Lomborg is incorrect because:

To put the analysis of Lomborg in an analogy: Say, we want to travel from Beijing to Paris and want to arrive in three weeks, in time for the COP. We have planned the route until Moscow and agree to plan the last part of the route further down the road. According to Lomborg, we will not arrive in Paris, because he assumes we do not only stop travelling in Moscow, but he also assumes we return and travel back east.

What CAT is doing is looking at whether we can be in time in Moscow (GHG emissions in 2030) to allow a timely arrival in Paris (keeping global temperature rise below 2°C by 2100).

The above issues are just some of the problems with the approach and method taken, but are the most fundamental.

Some of our colleagues from around the world have also taken a look at the study and come to similar conclusions: