Greta Thunberg has done her science homework
On 21st February 2019 the Swedish climate activist Greta Thunberg, 16, delivered a strong speech  at the European Economic and Social Committee in Brussels. Thunberg teamed up with IPCC  science and scientists and encouraged politicians to take urgent action to combat climate change.
Thunberg said that politicians should listen to scientists and ”follow the Paris agreement and the IPCC reports”. The speech was considered a success by eyewitnesses  and media .
We checked the science references in Thunberg’s speech for pedagogical use with top scientists from Finland.
First three of the four science-related claims below were found accurate. The fourth claim about ”a minimum of 80 % CO2 reduction by 2030” would have required more explanation. Overall, the combination of IPCC climate science and an empowered youth raising concerns about the future is powerful. Strong political messages cannot always be evaluated by fact-checking.
That said, Thunberg’s activism can be claimed to be evidence-based and backed by a number of world-class scientists, well worth a nomination for Nobel Peace Prize . As Thunberg claims, she has done her homework. However, defining exact reduction targets is difficult for scientists but important for politicians.
Greta science-based claims 21.2.2019 (full text here )
1. ”…by the year 2020 we need to have bended the emissions curve steep downward.”
2. ”According to the IPCC report we are about 11 years away from being in a position where we set off an irreversible chain reaction beyond human control.”
3. ”To avoid that unprecedented changes in all aspects of society\, [actions] need to have taken place within this coming decade\, including a reduction of our CO2 emissions by at least 50 % by the year 2030. And please note that those numbers do not include the aspect of equity\, which is absolutely necessary to make the Paris agreement work on a global scale\, nor do they include tipping points or feedback loops like the extremely powerful methane gas released from the thawing Arctic permafrost. They do\, however\, include negative emission techniques on a huge planetary scale that is yet to be invented\, and that many scientists fear will never be ready in time and will anyway be impossible to deliver at the scale assumed.”
4. ”We have been told that the EU intends to improve its emission reduction targets. In the new target\, the EU is proposing to reduce its greenhouse gas emissions to 45 % below 1990’s level by 2030 . Some people say that is good or that is ambitious. But this new target is still not enough to keep global warming below 1.5 degrees Celsius. This target is not sufficient to protect the future for children growing up today. If the EU is to make its fair contribution to staying within the carbon budget for the two-degree limit\, then it means a minimum of 80 % reduction by 2030 and that includes aviation and shipping. So [it is] around twice as ambitious as the current proposal.”
The two independent scientists involved with IPCC were asked to review Greta’s public speech for science-based claims. They are:
Christian Breyer,  Professor of Solar Economy, LUT University
“I can clearly approve her Brussels speech from a scientific point of view, every single sentence. Specifically about the fourth claim on 80 % reduction target: this is part of interpretation, but let me explain. The remaining GHG emission budget is rather ’large’, in case we would like to reach the target with a 50 % probability. For a 66 % probability of target reaching the remaining GHG emissions are much lower (more than linear reduction), but to be on the safe side one should go for a 90 % probability to reach the target. The latter implies a very fast and very deep GHG emission reduction, even more drastic than mentioned by Greta. Now the relevant comparison: the Boeing 737 Max 8 is on ground after two strange crashes, but for all passengers in all flights in all of these planes the security had been higher than 99.9 %. This is a very high level of security. Honestly, for surviving on our planet, we should have the same drastic measures, if not more drastic. In other words, to really achieve the 1.5 C target in a very high probability the targets should be even more drastic, i.e. deeper and faster defossilisation than claimed by Greta. Thus the claim is more than fine.”
Markku Ollikainen,  Professor of Environmental and Resource Economics, University of Helsinki & Chair of Finnish Climate Panel “I agree on the general approach and arguments 1 - 3, but based on the climate research and data given by Greta statement I cannot fully confirm nor reject claim 4 on minimum 80% EU reduction target by 2030, as the fairness principle behind the calculation is not explicated.”
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