“All our expert witnesses say treating the most severe trajectory, RCP 8.5, as the “business as usual” baseline scenario was wrong. That placed us in the spotlight and as a result, our climate modelling has put too much emphasis on an unlikely scenario. ”
Have our climate models been wrong? This is the title of a new episode of the BBC World Service’s “The Inquiry”, available here on BBC sounds. It’s about the emphasis on RCP 8.5, often misleadingly referred to as “business as usual”.
After introducing the topic via James Hansen’s call to action in 1988, and the formation of the IPCC, the presenter says that some scientists are saying too much emphasis has been put on the worst case scenarios.
Four expert witnesses are presented. The first is Chelsea Harvey, a reporter for E&E News, who introduces the RCP scenarios, explaining that RCP 8.5 is a worst case scenario based on rapid expansion of coal use. She says it’s human nature to be attracted to the worst case scenario.
Expert number two is Justin Ritchie, who says he started to question why RCP 8.5 was getting so much attention while he was doing his PhD.
Next up is Roger Pielke Jr, who says the proliferation of use of RCP 8.5 is a prime example of the misuse of science.
We got off track when we started treating scenarios not as scenarios of the future but as predictions or projections of the future.
When academics such as myself publish papers and university press offices put out press releases, you can be guaranteed that the most notable newsy studies will be those that employ RCP 8.5, and somewhere – I don’t think any of this is conscious, but somewhere along the way we take a scenario that is highly improbable, highly unlikely, and it goes through the process and shows up on the BBC or the front page of the New York Times as “where we’re headed” stripped of all the context and details, because it is a complicated topic, and if we repeat that hundreds of times, every year for the last decade, we get a picture of climate change that is not necessarily in conformance to what the broader literature actually says.
The analogy I often use in these situations was the decision to go to war in Iraq. In the short term there was a lot of fear generated by raising concerns of weapons of mass destruction and in fact it did lead to short term action with long term consequences – the invasion of Iraq. Later when it was discovered that the intelligence wasn’t quite sound, and may have had some political influence, there was a lot of lost credibility among the intelligence community, but also those politicians and policy makers who had pushed very hard for action based on the science. We shouldn’t evaluate science buy the worthiness of the cause, because that doesn’t lead to good decision making.
The continued use of RCP 8.5, and presenting it as business as usual, gives ample fodder for those who are opposed to action on climate change to criticise the scientific community, and they will be in real respects standing on solid ground when they do so.