December 2007

Climate Science blog

On August 8, 2007, I posted here a guest blog entry on the possibility that our observational estimates of feedbacks might be biased in the positive direction. Danny Braswell and I built a simple time-dependent energy balance model to demonstrate the effect and its possible magnitude, and submitted a paper to the Journal of Climate for publication.

The two reviewers of the manuscript (rather uncharacteristically) signed their names to their reviews. To my surprise, both of them (Isaac Held and Piers Forster) agreed that we had raised a legitimate issue. While both reviewers suggested changes in the (conditionally accepted) manuscript, they even took the time to develop their own simple models to demonstrate the effect to themselves.

Of special note is the intellectual honesty shown by Piers Forster. Our paper directly challenges an assumption made by Forster in his 2005 J. Climate paper, which provided a nice theoretical treatment of feedback diagnosis from observational data. Forster admitted in his review that they had erred in this part of their analysis, and encouraged us to get the paper published so that others could be made aware of the issue, too.

And the fundamental issue can be demonstrated with this simple example: When we analyze interannual variations in, say, surface temperature and clouds, and we diagnose what we believe to be a positive feedback (say, low cloud coverage decreasing with increasing surface temperature), we are implicitly assuming that the surface temperature change caused the cloud change — and not the other way around.

This issue is critical because, to the extent that non-feedback sources of cloud variability cause surface temperature change, it will always look like a positive feedback using the conventional diagnostic approach. It is even possible to diagnose a positive feedback when, in fact, a negative feedback really exists.

I hope you can see from this that the separation of cause from effect in the climate system is absolutely critical. The widespread use of seasonally-averaged or yearly-averaged quantities for climate model validation is NOT sufficient to validate model feedbacks! This is because the time averaging actually destroys most, if not all, evidence (e.g. time lags) of what caused the observed relationship in the first place. Since both feedbacks and non-feedback forcings will typically be intermingled in real climate data, it is not a trivial effort to determine the relative sizes of each.

While we used the example of random daily low cloud variations over the ocean in our simple model (which were then combined with specified negative or positive cloud feedbacks), the same issue can be raised about any kind of feedback.

Notice that the potential positive bias in model feedbacks can, in some sense, be attributed to a lack of model “complexity” compared to the real climate system. By “complexity” here I mean cloud variability which is not simply the result of a cloud feedback on surface temperature. This lack of complexity in the model then requires the model to have positive feedback built into it (explicitly or implicitly) in order for the model to agree with what looks like positive feedback in the observations.

Also note that the non-feedback cloud variability can even be caused by…(gasp)…the cloud feedback itself!

Let’s say there is a weak negative cloud feedback in nature. But superimposed upon this feedback is noise. For instance, warm SST pulses cause corresponding increases in low cloud coverage, but superimposed upon those cloud pulses are random cloud noise. That cloud noise will then cause some amount of SST variability that then looks like positive cloud feedback, even though the real cloud feedback is negative.

I don’t think I can over-emphasize the potential importance of this issue. It has been largely ignored — although Bill Rossow has been preaching on this same issue for years, but phrasing it in terms of the potential nonlinearity of, and interactions between, feedbacks. Similarly, Stephen’s 2005 J. Climate review paper on cloud feedbacks spent quite a bit of time emphasizing the problems with conventional cloud feedback diagnosis.

I don’t have an answer to the question of how to separate out cause and effect quantitatively from observations. But I do know that any progress will depend on high time resolution data, rather than monthly, seasonal, or annual averaging. (For instance, our August 9, 2007 GRL paper on tropical intraseasonal cloud variability showed a very strong negative cloud “feedback” signal.)

Until that progress is made, I consider the existence of positive cloud feedback in nature to be more a matter of faith than of science.

So-called Global Warming has the potential to destroy 300 years worth of scientific progress and our advanced western civilization along with it. From an economist’s position, it is pure folly. And our worst enemies’ dream come true.

Not So Hot

by Julie Walsh on December 31, 2007

in Blog

If a scientific paper appeared in a major journal saying that the planet has warmed twice as much as previously thought, that would be front-page news in every major paper around the planet. But what would happen if a paper was published demonstrating that the planet may have warmed up only half as much as previously thought?

The Biggest News of the Year

by Julie Walsh on December 31, 2007

According to Bill McKibben in an op-ed in The Washington Post, the biggest news of the year is that Jim Hansen has spoken. According to Hansen, who has risen in recent years from astronomer to wizard and now to high priest of a doomsday cult, the safe level for carbon dioxide in the atmosphere can be no more than 350 parts per million.  So since it’s now 380 or 390 ppm, we’re already doomed and can stop worrying about it.

Oh, no, sorry, we can’t stop worrying about it. True, we’re just about cooked (like Hansel and Gretel in the oven), but there’s still barely time to save life on Earth if we turn off the lights and throw away the car keys this instant. The alternative, I guess, is to party now for tomorrow we die. Hmm, I can’t decide. What if there’s just a tiny chance that Hansen could be wrong? Wouldn’t drastically reducing our energy consumption cause colossal increases in human mortality and suffering?

The course of apocalyptic movements is generally similar. In order to keep the enthusiasm of its followers at a fever pitch and to attract new followers, it is necessary to keep stoking the fires with more and more outlandish claims. The hysteria peaks as doomsday is moved closer and closer to the present, and then — poof — it collapses. It appears to me that the global warming bubble has gone about as far as it can go before it descends into ranting and writhing on the ground or random outbreaks of mob violence.

Unfortunately for Hansen and McKibben as with so many previous prophets of the end of the world, reality isn’t cooperating with their chiliastic fantasies. Atmospheric concentrations of CO2 have increased by 4 per cent since the Kyoto Protocol was negotiated in 1997, but the global mean temperature has been flat since 1999. What they must have are some big disasters — and soon.

Economist Gwyn Prins from London School of Economics got his turn at Nature Podcast's Podium on October 25. He is outlining an agenda for the Bali conference that makes sense to those of us who has a vested interest in results, rather than a vested interest in status quo. The speech is based on a paper he and a colleague published in Nature that same week, but alas, the politicians at Bali don't read Nature, that means they have to sit down and understand science and stuff, which is too much to ask a meager politician about…

In December, the world's politicians, the climate policy community, activists, NGOs, and an army of attended media will converge on the Indonesian Island of Bali for the most important summit on climate change since Al Gore rescued the Kyoto protocol ten years ago. The Bali conference will decide the international climate policy for the years after 2012 when the protocol expires. The Bali agenda shows that unless something happens to stop it the plan is for a bigger and better Kyoto with more stringent targets, more ambitious timetables, more carbon trading, more countries inside the UN process. If that agenda is successfully achieved at Bali then ironically humanity will lose an important opportunity to start to make an impact on anthropogenic aspects of global climate change. Why? Because Kyoto has failed; it is time to ditch Kyoto, cut our losses, and to radically rethink climate policy. In this week's Nature, Steve Rayner and I outline the story of Kyoto's failure and also state a handful of key principles to underpin a radical and practical rethink. These should frame the Bali agenda. What failure? Kyoto's supporters may ask. Since coming into effect, Kyoto has produced no demonstrable reductions in emissions or even in anticipated emission's growth and it pays no more than token attention to the needs of societies to adapt to existing climate change, but the present moment is more precarious still. For Kyoto's continued policy failure is being spun by signatory governments, especially in Europe as a story of success. The danger is that while today there is strong public support for climate action, when the truth about the failure of Kyoto's admitted as circumstances will oblige, we may experience public withdrawal of trust and consent for action whatever form it takes. Kyoto's supporters often blame non signatory governments, especially the United States and Australia for its vows, but the Kyoto protocol was always the wrong tool for the nature of the job. Kyoto was constructed by quickly borrowing from past treaty regimes dealing with stratospheric ozone, acid rain from sulphur emissions, and nuclear bombs. Drawing on those plausible, but partial analogies Kyoto's architects assumed that climate change would be best attacked directly through global emissions controls, treating tons of carbon dioxide like stockpiles of nuclear weapons to be reduced via targets and timetables. Kyoto relied on firing a silver bullet. The top down creation of a global carbon market, but there is little sign of any stable global carbon price emerging for the next decade or so and certainly not with a price signal strong enough to drive innovation. In the final analysis, carbon's trade cannot deliver the escape velocity required to get investment in technological innovation into orbit in time. That calls as we do for putting investment in decarbonised energy technologies on a wartime footing. Otherwise, they will not be available in time to disrupt the impending cycle of new investment in carbon intensive infrastructure and present cause, we are all about to be hit by a tidal wave of coal, especially in China, but a new Apollo or Manhattan project is only one of the necessary principles. No single shot can work on a complex open system issue like this. What we need is not a silver bullet, but silver buckshot. What Bali needs is a portfolio of approaches to move us in the right direction of which decarbonising the energy cycle is only one.

October 4th was Bjørn Lomborg's turn at Nature Podcasts' Podium. I listened to this podcast only last week, because I have been a bit backlogged with my science podcast listening.

"Prioritization is an integral part of life. We budget, money, and time because they are limited. In the hospital's emergency room, doctors use prioritization or triage to save lives, but we do not use prioritization when we grapple with the world's biggest problems. We know that carbon emissions cause climate change. So, activists urge us to make drastic cuts in the CO2 we pump out, yet climate change is not the only problem facing the planet, malaria, malnutrition, and HIV/AIDS claiming millions of lives right now. In an ideal world, we would have the money and the time to solve all these problems at a stroke. In real life, we do not. Pretending that we can do everything often just means that our money and attention goes to the problems with the loudest cheerleaders or the most media attention. We need to consider how far we should push a particular solution, making drastic cuts to carbon emissions, similar to making drastic cuts to the speed limits on our roads. Slowing traffic to a crawl would save millions of lives. We could wipe out almost all road deaths overnight, yet we reject such a drastic step as nonsensical because we accept that it would make modern life impossible. That does not mean we let cars go as fast as they want. As societies, we have decided on an appropriate speed limit for our highways after weighing up the benefits we get from the efficient transport of people and goods and then considering the number of accidents. Now, we need to have a discussion about carbon emission reductions. Likewise, we should be talking about what we are willing to sacrifice and what we hope to gain. I believe this discussion should not be left just to climate scientists. We all need to look at the wider picture and remember that global warming is not the only problem facing the planet. We should be asking what policies will best help the world overall. The answers might sometimes be surprising, as an example, we often hear that rising temperatures will mean more malaria. This is true. But are CO2 cuts the best way to help people? For every person saved from malaria through the curative protocol the same resource is spent on mosquito nets and medication could save 36,000 people. Just as there are many problems facing the planet there are many possible solutions to those challenges. My belief is that immediate carbon emission cuts are not the best way to respond to climate change, instead I believe we should invest heavily in the research and development of non-carbon emitting energy technologies which will give our kids and grandkids and China and India inexpensive tools to fix climate change by mid century while allowing for the continued development of human welfare."

Scientists like money. (It's true — be still, my heart.) Big Science is a Big Business, supporting nearly half the budgets of our major universities. Science professors are only hired if they can swing enough Federal grant money to pay for their labs, hire a gaggle of graduate assistants, and let the universities skim up to forty percent off  the top for overhead.

A Nation of Dim Bulbs

by William Yeatman on December 26, 2007

in Blog

Ahnuld’s Folly

by Julie Walsh on December 26, 2007

in Blog

New Yorkers should rejoice that the Environmental Protection Agency last week slapped down California's request to write its own fuel-economy rules to combat global warming. Gov. Spitzer had vowed to follow the lead of California's Arnold Schwarzenegger – so if the "Governator" had prevailed, New Yorkers would have seen their wallets and their cars shrinking.