AGW skeptics Dec 9 UN letter - rebuttal

To debate with climate change deniers is like fighting a Hydra - cut off one head, and the same point pops up somewhere else in the media.

We need a battlefield where we can meet and defeat them face to face.
They have now presented us with such a battlefield.

On December 9th the "Climate Realist" website carries a letter to Ban Ki Moon, with a challenge to us, and the usual list of signatories.

They will have given this letter their best shot, presenting their full and definitive case, so we should make an effort to rebut all their points fully, and put it out to the media.

Below, their text is in italic, and my response in normal font.

Specifically, [they] challenge supporters of the hypothesis of dangerous human-caused climate change to demonstrate that:

"1 Variations in global climate in the last hundred years are significantly outside the natural range experienced in previous centuries;

2 Humanity’s emissions of carbon dioxide and other ‘greenhouse gases’ (GHG) are having a dangerous impact on global climate;
The only explanation of current abnormal temperatures is the input of man-made CO2.

3 Computer-based models can meaningfully replicate the impact of all of the natural factors that may significantly influence climate;
See here

4 Sea levels are rising dangerously at a rate that has accelerated with increasing human GHG emissions, thereby threatening small islands and coastal communities;

Acknowledgements to Robert Rohdes, Global Warming Art

5 The incidence of malaria is increasing due to recent climate changes;
This is a red herring. Although malaria incidence is predicted to rise with global temperature, malaria incidence figures are tied in with the medical effort to identify and treat the disease, the success of treatment, the speed at which infected mosquitoes can colonise new areas, the success of swamp eradication measures and other factors. Deniers now accept that climate change is happening; they must therefore accept that the prevalence of malaria-risk areas will increase.

6 Human society and natural ecosystems cannot adapt to foreseeable climate change as they have done in the past;
In the past, humans had to migrate away from excessive heat or cold. The same thing is going to happen in the future if climate change continues, but we also have the knowledge and power now (a) to stop making climate change worse by decarbonising, (b) to reduce levels by sequestration, and (c) to put in adaptive measures. Deniers want to skip (a) and (b). This is a very dangerous omission, for which the most plausible explanation is that it is politically driven, since decarbonisation will hit the oil companies who finance many deniers.

7 Worldwide glacier retreat, and sea ice melting in Polar Regions , is unusual and related to increases in human GHG emissions;

Glaciers are indeed in retreat. This is consistent with observed temperature rises, and we have shown above that temperature rises can only be explained by increases in human GHG emissions.

8 Polar bears and other Arctic and Antarctic wildlife are unable to adapt to anticipated local climate change effects, independent of the causes of those changes;
See here.
9 Hurricanes, other tropical cyclones and associated extreme weather events are increasing in severity and frequency;
Now this is interesting. The topic is still under debate, but indications are that there is a relationship between hurricanes intensity and temperature.

10 Data recorded by ground-based stations are a reliable indicator of surface temperature trends.
Difficult to know what they are driving at here, which is a bit poor, since they are communicating with the UN Secretary General. There are quite a few temperature monitoring stations to consider. Go here, scroll down to the thing that looks like a map of the world.

Their final shot is this:
It is not the responsibility of ‘climate realist’ scientists to prove that dangerous human-caused climate change is not happening. Rather, it is those who propose that it is, and promote the allocation of massive investments to solve the supposed ‘problem’, who have the obligation to convincingly demonstrate that recent climate change is not of mostly natural origin and, if we do nothing, catastrophic change will ensue. To date, this they have utterly failed to do so".

On this last point they are wrong, since the projected damages from climate change are so serious that there is a clear onus on the business as usual lobby, if their case is scientific, to present their case in a way that is capable of refutation.

They are simply being intellectually lazy here.

So this is a response to the best that the denial movement can offer, put together in a couple of hours by a scientifically - trained Green party member.

I hope that the community of climate scientists will issue an authoritative and definitive rebuttal that can be a standard reference point for media commentators on the ongoing debate, so that we can focus on this one document, as representing the deniers' very best effort, so that all this foot dragging nonsense can be left in the past.