An Eccentric Anomaly: Climate Change

Ed Davies's Blog


Pages tagged: Climate Change

Anthropogenic global warming and all that

Grid Intensity

There's a little group of people centred around the OpenEnergyMonitor project/products doing some very good work related to reducing carbon emissions over a wide range of scales from monitoring and control equipment that people can use in their own homes to supporting studies for CAT's Zero Carbon Britain project.

However, they do seem to me to have too much interest in the realtime carbon intensity of the UK grid (measured in kilograms of CO₂ emitted for each kilowatt hour of electricity generated). While looking at these figures can be educational, I think it's too easy for people to be mislead in a way which would actually increase emissions in the short term.

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What Hiatus?

It's widely supposed that temperatures over the last 16 years or so (since about 1998) have not risen, much. For example, a discussion of one such case: Global Warming Stopped in 1997, Yeah Right.

Yesterday Tamino published a blog post showing that actually, if anything, it's been generally warmer over this period than would be expected looking at a simple extrapolation of previous years: Global Temperature: the Post-1998 Surprise.

Of all pseudonymous bloggers, Tamino is one of the ones I'd trust most to be thorough and honest in presentation of a result like this. Still, there's always room for miscommunication and misunderstanding and this is, indeed, enough of a surprise to be worth some examination rather than just blind acceptance and repetition.

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Seasonal Sea Ice Variation

There's a certain sick fascination to be had watching the Arctic sea ice disappear over the years. The minimum extent (area of ocean covered by at least 15% ice) happens each year in September at the end of the melt season and it's preceded by a period of speculation as to what the cover will be this year. As well as the overall downward trends in the sea-ice extents there's also, of course, year-to-year variation.

What I wondered was, how early in the year do you get a reasonable idea of what the September extent could be, so I decided to plot a few graphs to have a look. For example, 2012 was a record low year which was preceded by a sudden drop in extent in early June. 2013 has been bouncing around in the same general ball-park as 2012 until the last few weeks where it hasn't followed last year's curve. (See the NSIDC daily graph for whatever's happening now.)

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David Rose Again

David Rose is at it again with this article in the Mail on Sunday. As with last time lots of people have expressed their displeasure at various points. To find this commentary a good place to start is the update to and comments on the post from which the graph at the top of the article was originally taken (here) but replaced with Comparing global temperature observations and simulations, again by Ed Hawkins on the Climate Lab Book blog.

I just want to focus on an answer to one particular point. More...

Carbon Dioxide and Seawater

Introduction

In the same Green Building Forum discussion as the previous comments about Stefan's Law, which I blogged about, Tony also made remarks about warming possibly causing the increase of CO₂ in the atmosphere rather than being the result of it. His idea seems to be that warming of the oceans causes them to be less able to dissolve CO₂ so it comes out of solution and bubbles up into the atmosphere.

...and the rises in the levels of CO2 could even be an effect of these rises rather the cause of them were the rises to be due to some other factor.
As the temperature of seawater rises we know that it can't hold so much dissolved CO2 so at least some of it must be a result of that.

I think this is ridiculous. Here's why.

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Stefan's Law and AGW

A while ago on the Green Building Forum, in the context of asserting that current theories of anthropogenic global warming are wrong, Tony wrote:

Finally any model that shows consistently rising temperatures or exponentionally rising temperatures must be ignoring Stefan’s Law which says that heat is lost in proportion to the fourth power of the absolute temperature, setting up a very strong force to stop or at least reduce any increases.

I think that's not right and I gave a quick response in the next post on that thread giving a “meta” reason why I thought so: that it's ridiculous to think that climate scientists aren't perfectly well aware of this law. Another quick near-meta argument I could have given is that feedback resulting from the supposed steep effects of Stefan's Law were not enough to prevent global temperatures dropping by around 6 °C during the last glacial maximum.

However, there's a physical reason, too, and the details are interesting enough that it seemed worth writing up my understanding of the situation.

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Global Warming Stopped in 1997, Yeah Right

David Rose, writing in the Mail on Sunday claims Global warming stopped 16 years ago, reveals Met Office report quietly released... and here is the chart to prove it. Lots of people have already bashed this but I think I can provide a perspective that might be helpful to some.

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Elsewhere

Some comments made on other people's blogs:

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Stratospheric Cooling

Last autumn I wrote a post on the Navitron forum about a reason for cooling of the stratosphere with increased carbon dioxide in the atmosphere. I later posted a reference to it in a comment on Kaitlin Alexander's blog (Climate Sight) which lead to further discussion which showed that what I described is only one of the mechanisms which tends to cause stratospheric cooling. In particular, Martin Vermeer's comment explains the other, perhaps the main, mechanism well.

Nevertheless, I'm sufficiently smug about my own explanation that I'm going to put a slightly-edited copy here.

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