Video description

On the 19th of July in 2011 the National Press Club of Australia held a debate on climate change. I will be analysing the claims Monckton made during the debate and if they are correct or not.

In this part of the debate Monckton cites a paper by Roy Spencer and his colleague Danny Braswell as evidence for a low climate sensitivity. What does this paper say and are these conclusions justified?

Transcript

We might also cite Spencer and Braswell, 2010, who have said similar things, having at last measured the cloud feedback and found it to attenuate global warming by as much as the IPCC had thought it increased it.

And here Monckton yet again picks one of the few papers that agrees with his position. Which is also just as flawed as the previous one he cited.

The so-called sceptics like Monckton often attack the best models we have. He did so in this very debate, where he said that “all the science done by measurement and observation rather than by models, suggests just one Celsius degree [for a doubling of CO2]”. Here's the relevant section of the debate where he said this:

And why do we think that we're going to suddenly get 3.3 Celsius for a doubling of CO2 concentration, this century, that's the IPCC's central estimate, or 5.1 which is your government's central estimate, when all the science done by measurement and observation rather than by models, suggests just one Celsius degree?

The salient detail here is that the paper he cites uses a model to determine climate sensitivity, a very simple model. Unfortunately it's too simple of a model to be used effectively, something Spencer has been criticised for.

However the biggest issue is with the suggestion in this paper that clouds will act as a strong negative feedback, meaning they would cool the planet. The problem with this is that it goes contrary to what we know about how clouds act on global temperatures. There is a lot of discussion on this subject, but no matter if it would amplify or negate some of the warming, the effect would be minor.

Spencer hasn't been able to prove this via this paper or any subsequent papers. A lot of his research has been dismissed by other scientists due to some very basic errors.

This again shows that the quality of the source Monckton cited is very poor, which undermines his argument that climate sensitivity is low.

Sources

1. A Determination of the Cloud Feedback from Climate Variations over the Past Decade
2. On the diagnosis of radiative feedback in the presence of unknown radiative forcing
3. Issues in Establishing Climate Sensitivity in Recent Studies
4. Cloud variations and the Earth’s energy budget
5. Relationships between tropical sea surface temperature and top‐of‐atmosphere radiation
6. An Even Cloudier Outlook for Low Climate Sensitivity

Media resources

1. NASA | Supercomputing the Climate