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Hit the brakes hard

Filed under: — group @ 29 April 2009 - (Español)

There is a climate splash in Nature this week, including a cover showing a tera-tonne weight, presumably meant to be made of carbon (could it be graphite?), dangling by a thread over the planet, and containing two new articles (Allen et al and Meinshausen et al), a “News & Views” piece written by two of us, and a couple commentaries urging us to “prepare to adapt to at least 4° C” and to think about what the worst case scenario (at 1000 ppm CO2) might look like.

At the heart of it are the two papers which calculate the odds of exceeding a predefined threshold of 2°C as a function of CO2 emissions. Both find that the most directly relevant quantity is the total amount of CO2 ultimately released, rather than a target atmospheric CO2 concentration or emission rate. This is an extremely useful result, giving us a clear statement of how our policy goals should be framed. We have a total emission quota; if we keep going now, we will have to cut back more quickly later.

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Friday round-up

Filed under: — rasmus @ 24 April 2009 - (Español)

They knew all along?
A recent story in NYT: ‘Industry Ignored Its Scientists on Climate‘ has caught our attention.

Update: Marc Roberts’ take:

Latest skeptical song from Singer

This week, the annual European Geophysical Union (EGU)’s general assembly was held in Vienna. Friday afternoon, I went to one of the conference’s last talks to learn about the latest news from the climate skeptics (have to keep an open mind…). It was probably the talk with the smallest audience in the whole conference (see the photo, but note there were a couple of individuals who were not captured by camera), despite an unusually long slot (30 min) allocation.

singer.jpg And not much news, I’m afraid, apart from that SEPP plans to release it’s NIPCC’09 in May. I understand it will be a thick report (800 pages?). The main messages were (a) that GHGs were unimportant – allegedlly supported by Douglass et al. (2007), and (b) solar activity was the main reason for the recent global warming and the mechanism involved galactic cosmic rays (GCR).

I asked Singer how he could explain the most recent warming when there is no trend in the GCR-flux or other indices of solar activity since 1952. He countered by saying he was glad I asked him this question, and announced that he had done his thesis exactly on the topic solar wind and GCRs.

So I had to answer that I had written a book about solar activity and climate, and I repeated my question. He could not answer in the end – other than saying that we have to look at the data. I told him that we already have looked at the data (e.g. Richardsson et al 2002; Benestad, 2005; Lockwood & Frohlich, 2007), so I recommended him to read up on RC.

Yet more aerosols: Comment on Shindell and Faluvegi

Guest post from Drew Shindell, NASA GISS

Our recent paper “Climate response to regional radiative forcing during the twentieth century”, has generated some interesting discussion (some of it very ‘interesting’ indeed). So this post is an attempt to give a better context to the methods and implications of the study.

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Aerosol effects and climate, Part II: the role of nucleation and cosmic rays

Filed under: — group @ 15 April 2009 - (Italian)

Guest post by Bart Verheggen, Department of Air Quality and Climate Change , Energy research Institute of the Netherlands (ECN)

In Part I, I discussed how aerosols nucleate and grow. In this post I’ll discuss how changes in nucleation and ionization might impact the net effects.

Cosmic rays

Galactic cosmic rays (GCR) are energetic particles originating from space entering Earth’s atmosphere. They are an important source of ionization in the atmosphere, besides terrestrial radioactivity from e.g. radon (naturally emitted by the Earth’s surface). Over the oceans and above 5 km altitude, GCR are the dominant source. Their intensity varies over the 11 year solar cycle, with a maximum near solar minimum. Carslaw et al. give a nice overview of potential relations between cosmic rays, clouds and climate. Over the first half of the 20th century solar irradiance has slightly increased, and cosmic rays have subsequently decreased. RC has had many previous posts on the purported links between GCR and climate, e.g. here, here and here.

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Aerosol formation and climate, Part I

Filed under: — group @ 13 April 2009 - (Italian)

Guest post by Bart Verheggen, Department of Air Quality and Climate Change , Energy research Institute of the Netherlands (ECN)

The impacts of aerosols on climate are significant, but also very uncertain. There are several reasons for this, one of which is the uncertainty in how and how fast they are formed in the atmosphere by nucleation. Here, in part I, I’ll review some of the basic processes that are important in determining the climate effects of aerosols, focusing in particular on their formation. This is also relevant in order to better understand –and hopefully quantify- the hypothetical climate effects of galactic cosmic rays which I’ll discuss in a follow-up post.

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