Dr James Renwick criticises Dr Chris de Freitas for keeping a cool head and saying there’s no need to worry about normal climate change. James says:
I am puzzled that de Freitas can review the evidence, the melting ice sheets, rising seas, warming oceans and atmosphere, and see nothing to worry about.
He claims four points of evidence. Let’s have a look at them.
Melting ice sheets
The AR5 will tell you that combined annual losses from surface melting and glacier calving on the Greenland and Antarctic ice sheets contribute about 1 mm per year to sea level rise (p 320). But it won’t tell you this is trivial, and it won’t tell you that the ice sheets will last many thousands of years before vanishing. I wrote a post on this three months ago. On recent figures, Antarctica has about 225,000 years to go, and Greenland will last another 9,400 years. Is James claiming that this rate of ice loss should cause concern?
There’s no evidence of acceleration in the long-term rate of sea level rise of about 1.8 mm/yr and, as chance would have it, news comes this week of four widely-spread studies published in the last few months that find no human influence in sea level rise. Pierre L. Gosselin summarises three of the papers:
Scientists who have recently attempted to detect an anthropogenic signal in regional sea level rise trends have had to admit that there is “no observable sea-level effect of anthropogenic global warming,” or that the “sea level rise pattern does not correspond to [an] externally forced anthropogenic sea level signal,” and that sea level “trends are still within the range of long-term internal decadal variability.”
The fourth paper concludes with a vexatiously enigmatic remark, that “this result is consistent with recent findings that beside the anthropogenic signature, a non-negligible fraction of the observed 20th [century] sea level rise still represents a response to pre-industrial natural climate variations such as the Little Ice Age” (emphasis mine). Did they detect an anthropogenic signature or not?
So I’ve sent Dr Dangendorf, lead author, an email:
I’m keen to obtain a copy of this recent paper. Your abstract concludes: “This result is consistent with recent findings that beside the anthropogenic signature, a non-negligible fraction of the observed 20th sea level rise still represents a response to pre-industrial natural climate variations such as the Little Ice Age.” So I’m particularly interested to know whether you could say that you found an anthropogenic “signature” in the sea level rise data or that you did not. If you have time, I would be most grateful for your comments.
Some are warming, some are cooling. Look at the data and you’ll find that different latitudinal bands are cooling and warming, different depth bands are cooling and warming. Different oceans are accumulating and dissipating heat. The picture is far from certain and far from alarming. Ocean heat content is no reason to worry about climate change.
The atmosphere has not warmed significantly for about 20 years. This graph of the UAH satellite record for the lower troposphere shows the temperature has not risen significantly since about 1997. It gives us no reason to worry.
What scientific evidence does de Freitas have that shows negative (cooling) feedbacks prevail?
First, 4.5 billion years of earth’s existence, during which enormous length of time positive feedbacks have never
occurred predominated. Second, I don’t know, since I haven’t spoken with him over this. Third, since it’s your assertion that positive feedbacks are about to occur, it’s your responsibility to provide evidence for it. What is it?
Positive feedbacks are clearly under way.
There is no evidence that positive feedbacks are under way. Can you provide any?
De Freitas states that there is no evidence to distinguish between “natural” and “human-caused” warming. There is an 86-page chapter on this topic in the last IPCC report, citing over 600 scientific papers on the subject. The conclusion was: “It is extremely likely that human activities caused more than half of the observed increase in Global Mean Surface Temperature from 1951 to 2010.” How can this be characterised as “no evidence”?
First, “extremely likely” only means that it’s possible, which doesn’t make it evidence. Second, the only indication, even in AR5, that human activity causes atmospheric warming is the output from unvalidated climate models, which doesn’t make it evidence. Please provide evidence of human-caused warming.