Email, Michael Tobis, research scientist, Dec. 10, 2013

On Mon, Dec 9, 2013 at 8:04 PM, Selby, Gardner (CMG-Austin) wrote:

If you have any thought and info related to Curry’s statement below, let me know?


From: Curry, Judith A

Sent: Monday, December 09, 2013 12:39 PM

To: Selby, Gardner (CMG-Austin)

Subject: Re: Texas reporter


There has been no statistically significant increase in global average surface temperatures for the past 17 years.

11:30 a.m.

Dec. 10, 2013

"statistically significant" = weasel words or confusion.


Statistical significance really implies having a large sample size and performing an experiment. There are people who talk about statistical significance of warming, but that really requires a lot of assumptions about the "null hypothesis". In this case it probably means "assuming that we had twenty otherwise identical planets that were not having a warming trend, and we looked only at the last 17 years of data with no other input, it is unlikely that more than one of them would be as warm as the one we are observing."

Now, there are a number of issues in how you would do the test even if you had the twenty planets, but there are ways to argue around this. The most important fact in looking at this claim is that 17 years is a short time. If you actually don't cherry pick your start date there is not much sign of a slowdown.

Recent corrections show that the "hiatus" is largely an artifact of under-weighting the Arctic in any case, and this illustrates how non-robust the hiatus is.

It is true that even so, the rate of warming that we observe recently is starting to look a bit less than predicted. It is early to bet the farm on this. One strong El Nino could make the data tell a very different tale.

There are strong indications that the deep ocean is heating more than anticipated, which would account for some missing warming at the surface. This is the explanation of what is going on that the scientific community seems to be focused on.

But it's crucial to understand this - the world has not wandered so far from what we expected as to require a deep reconsideration of the consensus. There's no doubt that CO2 is piling up in the atmosphere. There's no doubt that human activity caused it. There's no doubt that CO2 is a major factor in how energy flows through the climate system, and that changing it leads to a changed climate. There's practically no doubt that in the long run the planet will end up substantially warmer than it is. Figuring out how it gets from here to there matters a lot to human beings who live out our brief lives during the adjustment period. And there are some uncertainties there - it turns out transitions are harder to calculate than final outcomes. But nothing we see reduces our confidence in our understanding, and indeed the recent IPCC report is far less equivocal than previous ones that the evidence is coherent and clear.


What I wish you could do with your article is to convey what I think is the most important aspect that most people do not understand. That is that the problem is cumulative.

The amount of CO2 in the atmosphere changes very slowly via natural processes. So every bit we emit stays up there, and even if we reduce our emissions, it gets worse every year. We have to get emissions to zero to stop making matters worse. (Fortunately there are ways to accelerate the removal of CO2, but they are expensive, and so for practical purposes there is a global debt being accrued every time we burn any fossil fuel.)

This is the crucial aspect of the problem that people find the hardest to accept, and there is very little sign of it in the press so people aren;t even starting to think about it.