Greenhouse gases

Greenhouse gases help seasonal predictions

30 Nov 2005 by rasmus

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The conventional wisdom in meteorology has been that certain factors such as the complete oceanic state and the exact concentrations of greenhouse gases are of minor importance for a normal weather forecast. Moreover, whereas sea surface temperatures (SST) are important, the deep sea temperatures are believed to have little impact for predictions for the next few days. The reason is that the ocean reacts slowly to changes in the atmosphere (has much higher inertia and much higher heat capacity). Hence, the most important information needed for such a weather forecast is the atmospheric initial conditions, a description of what the atmosphere and the SST look like when the weather model starts computing the weather evolution.

650,000 years of greenhouse gas concentrations

24 Nov 2005 by Gavin

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The latest results from the EPICA core in Antarctica have just been published this week in Science (Siegenthaler et al. and Spahni et al.). This ice core extended the record of Antarctic climate back to maybe 800,000 years, and the first 650,000 years of ice have now been analysed for greenhouse gas concentrations saved in tiny bubbles. The records for CO₂, CH₄ and N₂O both confirm the Vostok records that have been available for a few years now, and extend them over another 4 glacial-interglacial cycles. This is a landmark result and a strong testament to the almost heroic efforts in the field to bring back these samples from over 3km deep in the Antarctica ice. So what do these new data tell us, and where might they lead? [Read more…] about 650,000 years of greenhouse gas concentrations

Busy Week for Water Vapor

21 Nov 2005 by raypierre

It’s been a busy week for water vapor, and I have two recent papers to discuss. The first is the paper "Anthropogenic greenhouse forcing and strong water vapor feedback increase temperature in Europe" by Rolf Philipona et al. (GRL, 2005, subscription required for full text), which has attracted a certain amount of media attention. The overall goal of the paper is to understand, from a physical standpoint, why European temperatures have been increasing three times faster than the Northern Hemisphere average. It focuses on the changes between 1995 and 2002, over which time good surface radiation budget observations are available. The paper reports some results on the role of large scale circulation changes (which they conclude are minor) but I’ll concentrate on the results relating to water vapor.

What is a first-order climate forcing?

22 Sep 2005 by Gavin

Roger Pielke Sr. (Colorado State) has a blog (Climate Science) that gives his personal perspective on climate change issues. In it, he has made clear that he feels that apart from greenhouse gases, other climate forcings (the changes that affect the energy balance of the planet) are being neglected in the scientific discussion. Specifically, he feels that many of these other forcings have sufficient ‘first-order’ effects to prevent a clear attribution of recent climate change to greenhouse gases.

In general, I heartily agree – other forcings are important, even essential, for understanding observed climate variability and, as a community, we are only just starting to get to grips with some of the more complicated effects. Obviously, though, not all forcings are of the same magnitude (either globally or regionally) and so it is useful to separate the ‘first-order’ forcings from those that are relatively minor. But what exactly is ‘first-order’ and what is not? [Read more…] about What is a first-order climate forcing?

Climate sensitivity and aerosol forcings

6 Jul 2005 by Gavin

In a new review paper in Nature this week, Andreae, Jones and Cox expand on the idea that uncertainty in climate sensitivity is directly related to uncertainty in present day aerosol forcing (see also this New Scientist commentary). This was discussed here a couple of months back in the Global Dimming and the climateprediction.net posts, and so it is worth revisiting the question in the light of their analysis.

The Acid Ocean – the Other Problem with CO2 Emission

2 Jul 2005 by david

The Royal Society has just issued a summary report on the effects of CO₂ on the pH chemistry of seawater and aquatic organisms and ecosystems. In addition to its pivotal role in the atmosphere in the regulation of global climate, CO₂ and its sister chemical species, HCO₃^– and CO₃^2- comprise the carbonate buffer system which regulates the pH of seawater. The new report can be found here. Acidifying the ocean is particularly detrimental to organisms that secrete shell material made of CaCO₃, such as coral reefs and a type of phytoplankton called coccolithophorids [Kleypas et al., 1999]. The ocean pH change will persist for thousands of years. Because the fossil fuel CO₂ rise is faster than natural CO₂ increases in the past, the ocean will be acidified to a much greater extent than has occurred naturally in at least the past 800,000 years [Caldeira and Wicket, 2003].

Make your own forecasts of future energy, carbon emissions, and climate

22 Jun 2005 by david

Over the years, IPCC has issued numerous scenarios describing the trajectory of civilization and what they may mean for CO2 emissions and the like. The most famous of these is the “Business-as-Usual” scenario, also called IS92A, although this has been supplanted somewhat by the SRES familiy of storylines that have been discussed here often.

While the different storylines and assumptions can be a little confusing, the ingredients for making such a forecast can be fairly simple, and I have coded them up into an interactive web site which can be used to explore the world of possibilities. The prediction is based on an idea called the Kaya identity, using numbers published by Hoffert et al. in Nature 1998 [Hoffert et al., 1998]. You could just read the excellent Hoffert et al. paper, but you might also enjoy playing with your own “live” forecasting model, located here.

How much of the recent CO₂ increase is due to human activities?

7 Jun 2005 by group

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Contributed by Corinne Le Quéré, University of East Anglia.

This question keeps coming back, although we know the answer very well: all of the recent CO₂ increase in the atmosphere is due to human activities, in spite of the fact that both the oceans and the land biosphere respond to global warming. There is a lot of evidence to support this statement which has been explained in a previous posting here and in a letter in Physics Today . However, the most convincing arguments for scientists (based on isotopes and oxygen decreases in the atmosphere) may be hard to understand for the general public because they require a high level of scientific knowledge. I present simpler evidence of the same statement based on ocean observations, and I explain how we know that not only part of the atmospheric CO₂ increase is due to human activities, but all of it.

2005 Record Arctic Ozone Loss

6 May 2005 by group

You read it here first!

Update (09/05/05): Markus Rex was kind enough to send us the full figure from which Nature made their thumbnail, and which is a little clearer. He also cautions that the 2005 numbers are still preliminary, however there is a clear trend towards increasing potential for Arctic ozone loss, which is realised or not depending on the vagaries of each individual winter.

Planetary energy imbalance?

3 May 2005 by Gavin

The recent paper in Science Express by Hansen et al (on which I am a co-author) has garnered quite a lot of press attention and has been described as the ‘smoking gun’ for anthropogenic climate change. We have discussed many of the relevant issues here before, but it may be useful to go over the arguments again here.

The key points of the paper are that: i) model simulations with 20th century forcings are able to match the surface air temperature record, ii) they also match the measured changes of ocean heat content over the last decade, iii) the implied planetary imbalance (the amount of excess energy the Earth is currently absorbing) which is roughly equal to the ocean heat uptake, is significant and growing, and iv) this implies both that there is significant heating “in the pipeline”, and that there is an important lag in the climate’s full response to changes in the forcing.

Greenhouse gases