Oct 01 2013

New IPCC Report on Climate Change

Whether or not the planet is warming due to human activity is a very important question. That is perhaps the one statement on which everyone agrees. Beyond that we have the usual conflict between mainstream science and motivated reasoning, denialism, industry apologists, and contrarians. Stuck in the middle are sincere skeptics who have not managed to wade through the tsunami of misinformation.

This is the 5th report of the intergovernmental panel on climate change (IPCC) assembled by the UN. The point of this panel is to provide usable information to the UN, and the governments of the world, through robust scientific consensus. They describe the working group as:

A total of 209 Lead Authors and 50 Review Editors from 39 countries and more than 600 Contributing Authors from 32 countries contributed to the preparation of Working Group I AR5.

That sounds pretty robust to me. Of course, consensus is not always correct in retrospect, but the whole point of building a consensus is that it is more likely to be correct than the quirky opinions of any individual or small group. Personal bias, error, skewed perspectives, and misinformation should all average out and the result should, hopefully, reasonably reflect the actual scientific evidence.

One core conclusion of the group is this:

Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.

Overall the IPCC has been fairly conservative in their conclusions. They felt confident, however, to label the basic fact that the planet is warming as “unequivocal.”

They also conclude (I summarize):

– The oceans are storing most of the extra heat, about 90%

– Arctic sea ice, Antarctic and Greenland ice caps, and Glaciers worldwide have all been losing mass

– Sea levels are rising

– Atmospheric CO2 and methane are at their highest levels in 800,000 years.

– This CO2 is causing increased atmospheric forcing (raising temperatures).

– And – Human influence is clear.

There are more points, adding detail to the above, but those are the big ones. Further, they have upgraded their overall confidence in anthropogenic global warming from 90% in the last report to 95% in the current one. The evidence for AGW, they argue, is getting stronger.

The response from the usual AGW deniers is predictable. The Mail Online, for example, published an article surrounding the comments of:

Amused: MIT climate professor Dr Richard Lindzen blasted the IPCC report, calling it ‘hilariously incoherent’

They refereed to Lindzen as “amused” throughout the piece. Lindzen is a long time AGW denier. Whenever you hear a report of a climate scientist skeptical of AGW, chances are good they are referring to Lindzen. His is definitely a minority opinion.

Don’t get me wrong, minority opinions are good in science. They keep the majority from getting complacent, and can provide a useful alternate view. I see the role of the minority opinion as being critical, in fact. That is why it annoys me all the more when those in the position of the opposition do such a terrible job.

In fact, I often gauge the credibility of the majority view by the quality of the opposition. If the opposition has some solid points to make, then maybe the majority view has some legitimate cracks in it and there is a genuine controversy. If the opposition continues to resort to tired fallacies, bad arguments, and distorted evidence, that only serves to increase my confidence in the consensus.

The Mail reports, for example:

‘Their excuse for the absence of warming over the past 17 years is that the heat is hiding in the deep ocean,’ the amused scientist said. ‘However, this is simply an admission that the models fail to simulate the exchanges of heat between the surface layers and the deeper oceans.’

This is one of the AGW deniers favorite current distortions. It has been dismantled repeatedly, and the fact that they desperately keep going back to this argument, without addressing the criticism of it, is very telling.

First, global warming has not paused. There is a background fluctuation to the overall upward trend in global surface temperatures. It is not legitimate to take recent data and proclaim a change in the overall trend, when that data is still compatible with the existing trend. We won’t know for another decade if the last decade’s data was simply the normal background fluctuation or a true change in the overall rate of temperature rise.

But – the most parsimonious conclusion at present is that the warming trend continues without significant change.

Further, it should be noted that surface temperatures are still warming, just not as fast as previously.

The second fallacy in this current AGW denying meme is that the data is referring to surface temperatures only – not the total amount of heat in the earth system. Most of the extra heat, 90%, in fact is stored in the oceans, and so relying on surface temperatures is looking at only a small slice of the total heat.

Lindzen tries to make it seem like this is an argument from ignorance – the heat is “hiding.” But this is not true. There is actually evidence that the deep oceans are warming.

Lindzen’s next ploy is to argue that what this really means is that the climate models are flawed – because the earth is not warming in exactly the same way as they predicted. This is similar to denying evolution because of some detail about the relationship between groups.  This is a classic denialist strategy – confuse uncertainty over the details of a complex theory with uncertainty about the core claims.

No one denies that climate models are imperfect and complex. Predicting exactly where all the heat will go and when is a pretty tall order for such models, and having to make some tweaks (more heat into the deep oceans, less into surface temperature, over a short period of time) does not call into question the bigger picture – the planet is warming due to forcing from human-released CO2.

The Mail article also makes this howler:

Dr Linzen’s derision of the IPCC report comes amid evidence that warming hasn’t occurred over the past 17 years, and that polar ice caps are even expanding.

I already dealt with that issue here. 

Seriously, if that’s the best they can do, I will take the consensus opinion of hundreds of climate scientists working over years to hammer out a conservative evaluation of the evidence.

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