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The research below, which I blogged from the AGU conference in December, is published today in Nature [subscription].

New research presented at the AGU today suggests that the entire Antarctic continent may have warmed significantly over the past 50 years. The study, led by Eric Steig of the University of Washington in Seattle and soon to be published in Nature, calls into question existing lines of evidence that show the region has mostly cooled over the past half-century. [Update: To be more specific here, incomplete records previously suggested that the interior was cooling].

Steig and colleagues combined satellite thermal infra-red collected over 25 years with weather station data for the region. Although the satellite data span a shorter time period and are accurate only for blue sky days i.e. when there is no cloud cover, they provide high spatial coverage of the region, which cannot be obtained from discrete ground measurements. In contrast, the weather station data provide complete temporal resolution over the past half-century.

Using an iterative process to analyse the data, they found warming over the entire Antarctic continent for the period 1957-2006. Restricting their analysis to 1969 to 2000, a period for which other studies have found a net cooling trend, Steig’s study found slight cooling in east Antarctica, but net warming over west Antarctica.

As well as uncovering evidence of warming over a wider region than previous studies have shown, the researchers found that warming occurred throughout all of the year and was greatest in winter and spring. In contrast, cooling over east Antarctica was restricted to autumn.

Continue reading "AGU 2008: Evidence that Antarctica has warmed significantly over past 50 years [updated]" »

Posted by Olive Heffernan on January 21, 2009
Categories: AGU, Cryosphere, Olive Heffernan | Permalink | Comments (19) | TrackBacks (1)

What do Boston, London, New York, Frankfurt, San Francisco, and Paris have in common? They have all been destroyed by asteroid impacts—in the movies. The death toll was enormous in every case. Understandably, people are worried that such a catastrophe might actually occur within their lifetime.

Actually, says climate scientist Mark B. Boslough, “if you’re going to stay up late at night worrying about something, worry about climate.” Boslough, a researcher at the Sandia National Laboratories in Albuquerque, New Mexico, US, says, “you are much more likely to die from climate change than from an asteroid impact by a factor of something like a thousand.” He presented his findings at the Fall Meeting of the American Geophysical Union in San Francisco, California.

Boslough cannot put a precise number on that ratio, because climate science is still replete with gaps in the relevant data. He is much more confident about the asteroid threat, though. He says that there is no evidence that anyone has died from an asteroid or meteorite impact—ever. He does not make a distinction between asteroids and meteors, saying the latter are basically fragments of the former and there is no size boundary to distinguish one from the other.

Looking at worst case scenarios for asteroid impacts and climate change over the next 100 years, Boslough estimates that the largest asteroid to impact Earth would be around 50 metres in diameter. It would explode in the atmosphere and not make an impact crater, he says, and it would kill no one. Asteroids larger than 50 metres across and likely to cross Earth’s orbit are rare, and the larger they are, the rarer they are. They are also well tracked. Smaller ones are more numerous, but even less likely to cause death and destruction on Earth.

Continue reading "AGU 2008: Asteroid impacts and climate change: which is the greater threat?" »

Posted by Olive Heffernan on December 19, 2008
Categories: Recent contributors, AGU, Communicating Climate Change, Earth science, Harvey Leifert, Society | Permalink | Comments (1) | TrackBacks (0)

Cross-posted from In the Field

This according to Stanford University researcher Mark Jacobson, who has compared various energy technologies in terms of not only greenhouse gas emissions but also conventional pollutants, land use, water resources and more. Speaking after a news conference here, Jacobson said he is trying to provide a more holistic analysis of the various energy options. "There's a lot of misinformation out there," he said.

A few of the key results follow:

Life cycle emissions -- Wind and solar thermal come out on top; tidal, wave and hydro all beat out solar photovoltaics, geothermal and nuclear, thanks to energy spent on equipment and installation; coal was the big loser, even with carbon sequestration (CCS), thanks to energy spent on mining and transport.

Mortalities due to air pollution from US vehicles -- For gasoline, projected deaths drop from 20,000 to 15,000 annually in 2020 due to improved technology and air quality standards. That figure would remain steady or perhaps even rise if ethanol (corn or otherwise) made up 85 percent of the transport fuels. Assuming electric transport takes off, wind reduces mortalities to almost zero, although the full suite of renewables fared almost as well. Coal with CCS would cut mortalities by upward of two-thirds. Nuclear falls between coal and renewables (assuming non-proliferation regimes hold and there aren't any explosions).

Footprint required to power US vehicle fleet -- Accounting for the base of the turbine alone (not roads), wind could power the entire vehicle fleet using less than 3 square kilometers of land. Corn ethanol and concentrated solar power are the big losers, with each requiring a chunk of land that is larger (and perhaps significantly larger) than the state of California.

Water usage -- Wind, solar photovoltaic, geothermal, tidal and wave all come in around zero; coal, nuclear and concentrated solar do well; hydropower gets a poor rating, thanks to evaporation rates from reservoirs (Jacobson divvies up the losses among energy and other uses). But the clear loser is ethanol, whether the source is corn or something else.

Jeff Tollefson

Posted by Olive Heffernan on December 19, 2008
Categories: AGU, Energy, Jeff Tollefson, Technology | Permalink | Comments (1) | TrackBacks (0)

As speculation grows that agreeing a global deal on climate change may extend well beyond the 2009 deadline, the risk of overshooting the EU’s target to limit the increase in global temperature to 2°C over pre-industrial levels looks increasingly likely.

The target is based on scientific evidence that below a 2°C increase, some of the worst impacts of climate change would be avoided. In its fourth assessment report, the IPCC calculated that limiting warming to that extent would mean stabilizing atmospheric concentrations at roughly 450 ppm CO2-equivalents.

But it’s clear at this year’s AGU that much uncertainty, and disagreement, remains on whether 2°C is an appropriate target and on the atmospheric greenhouse gas concentrations that equate to a given amount of warming.

Speaking here yesterday, James Hansen, director of the NASA Goddard Institute of Space Studies, called for atmospheric greenhouse gas concentrations to be restricted to 350ppm. Hansen also recently advised the UK government’s Environmental Audit Committee that the 2°C target should be revised to a 1°C increase above pre-industrial levels. Meanwhile, many of the scientists presenting work here are wrangling with whether stabilizing at 450ppm – or higher – is economically and technologically feasible.

The debate on where to stabilize is largely due to what Stanford’s Stephen Schneider dubs ‘double-barrelled uncertainty’ a term that encompasses the unknown factor in how far we can reduce emissions and in how the climate system will respond to any reductions we make.

The latter uncertainty – that inherent in the system – is measured in terms of climate sensitivity i.e. how much warming would occur if atmospheric GHG concentrations were doubled. This is currently estimated at 2-4.5°C, but Schneider said here on Tuesday that it’s more important for society to know the uncertainty around this range i.e. the chance that we will see a much larger degree of warming than anticipated for various atmospheric concentrations.

Given the fact that a massive reduction in emissions in the coming decades it is very unlikely, he says, and the fact that we could overshoot our target anyway, we need to take a serious look at the consequences. Schneider suggests that the IPCC should take it on board to evaluate climate scenarios for overshooting to 600 ppm and then subsequently reducing atmospheric concentrations to say 500ppm or 450ppm.

Continue reading "AGU 2008: Uncertainty and overshooting 2°C" »

Posted by Olive Heffernan on December 18, 2008
Categories: AGU, Climate Science, Climate prediction, GHG emissions, Olive Heffernan | Permalink | Comments (4) | TrackBacks (0)

Whether peak oil is good news for the climate ultimately depends on what replaces oil as our staple fuel source. It will be unsurprising to most that replacing dwindling oil reserves with coal would do little to solve the climate problem, but how much coal remains is also highly uncertain, according to Prof. David Rutledge of Caltech, who spoke to the press at the AGU this morning.

Andy Dessler of Texas A&M touched on this in a guest commentary posted here last month. In short, Dessler called for a global IPCC-like assessment of our fossil fuel reserves, pointing to a new analysis by Rutledge that shows the world’s available coal reserves are far lower than traditional estimates would suggest. If Rutledge’s estimates are correct, combustion of all remaining conventional oil, gas, and coal reserves would produce an atmospheric concentration of carbon dioxide of approximately 470 ppmv in 2100, near the stabilization target that many climatologists argue we must achieve to avoid the worst impacts of climate change.

While Rutledge’s estimates suggest that the worst-case scenarios of the IPCC may be unachievable, Ken Caldeira of Washington’s Carnegie Institute had a more sobering message. Caldeira and colleagues used a climate and carbon cycle model to look at how running out of oil could affect future climate scenarios. Their analysis showed that if we replaced oil with liquefied coal fuel promptly, we would reach 2°C above pre-industrial temperatures in 2042 instead of 2045. Replacing oil with renewables, however, would delay reaching 2°C above pre-industrial temperatures by 11 years. This is simply because per coal emits more carbon dioxide per unit of energy than oil; add to that the energy costs associated with conversion of coal to liquid fuels, a likely option if we run out of oil.

Continue reading "AGU 2008: Peak fuel reserves " »

Posted by Olive Heffernan on December 17, 2008
Categories: AGU, Climate prediction, Energy, GHG emissions, Olive Heffernan | Permalink | Comments (2) | TrackBacks (0)

I hadn’t anticipated quite so much rain during the AGU’s Fall conference in San Francisco, but apparently this exact week is, on average, the city’s wettest of the year. Or so I heard at today’s session on how the region is likely to be impacted by climate change.

California has been long recognized as a leader on climate policy, both on the home front and even internationally. It passed its first climate bill twenty years ago and just last week, the state adopted the nation's most sweeping climate action plan to date, pledging to cut its greenhouse gas emissions by 15% by 2020.

A close look at how the region is expected to fare under various warming scenarios makes its leadership in this arena look a lot like common sense. While temperatures in California are expected to increase in line with global averages, more worrying for the state is the projected water shortages, according to Dan Cayan of the Scripps Institution of Oceanography in La Jolla, San Diego, who spoke at AGU today. California faces the possibility of a 10% decrease in precipitation over the course of the century and could concurrently lose half of its late spring snowmelt. That's bad news for a region that is already heavily reliant on external water sources.

Sea-level rise will also be part of the equation, especially for the numerous coastal properties with little protection, said Peter Gleick, president of the Oakland, California –based Pacific Institute. Should those in the interior think they’re better off, though, climate models show that inland regions will warm more rapidly than the coast and will likely be more populated in the future owing to lack of available living space on the coast.

Continue reading "AGU 2008: On the home front" »

Posted by Olive Heffernan on December 17, 2008
Categories: AGU, Adaptation, Climate prediction, Extreme Events, Olive Heffernan | Permalink | Comments (0) | TrackBacks (1)

This evening at AGU there was a special screening of Crude, a film about our love affair with petroleum– oil that is, black gold, Texas tea.

The documentary won Richard Smith of the Australian Broadcasting Corporation this year’s AGU Walter Sullivan Award for Excellence in Science Journalism, a prestigious prize for outstanding reporting that makes geophysical science accessible and interesting to the general public. In Crude, Smith explores the geological formation of oil, its discovery and ascendancy in society and the potentially catastrophic consequences of our absolute dependence on it. Ironically, the very conditions under which oil was originally formed – a greenhouse world with elevated CO2 levels – are exactly those that its consumption could return us to.

Smith does an excellent job of conveying how oil, formed from the compressed remains of tiny plants and animals, could cause the demise of the most sophisticated species to have ever lived. And although we may be running out of the stuff, its pervasiveness in society means that weaning ourselves off oil will be no mean feat. There are no clear estimates of exactly how much oil is left in the ground, but the overwhelming message in Crude is that there are easily enough fossil fuel reserves to radically alter our climate should we use them all.

Overall, well worth a watch…

Olive Heffernan

Posted by Olive Heffernan on December 16, 2008
Categories: AGU, Communicating Climate Change, Energy, Olive Heffernan, Reviews | Permalink | Comments (1) | TrackBacks (0)

Over the past 24 hours, some 15,000 earth scientists descended on San Francisco for the annual Fall conference of the American Geophysical Union. Delegates were a dead give away at the airport and on the BART yesterday with their large poster tubes in tow. It’s my first AGU and it could be the jet lag, but I’m feeling slightly overwhelmed by the sheer size and number of parallel sessions; at any given time I could be at one of at least four climate-related talks and invariably find myself wondering why the session next door is receiving louder applause.

A number of talks today focused on the need for climate science to become less curiosity driven and more specific to the needs of stakeholders such as local authorities and natural resource managers.

This is a topic that’s been getting a lot of attention recently. Earlier this year, for example, scientists called for a billion dollar investment in climate computing facilities to enable regional scale climate predictions on decadal time scales. At a press conference this morning, scientists including Jonathan Overpeck from the University of Arizona and Jack Fellows of UCAR highlighted the importance of partnerships between universities and decision makers in enabling states and regions to plan for climate change.

Continue reading "AGU 2008: conference kicks off " »

Posted by Olive Heffernan on December 16, 2008
Categories: AGU, Climate prediction, Features, Olive Heffernan, Regional climate, Research | Permalink | Comments (3) | TrackBacks (0)

I'll be heading to the 2008 AGU Fall meeting this weekend.

Join me here next week for daily climate coverage from the largest annual earth science event, taking place this year in San Francisco from December 15-19.

Posted by Olive Heffernan on December 10, 2008
Categories: AGU, Olive Heffernan | Permalink | Comments (0) | TrackBacks (0)

American Geophysical Union meeting, San Francisco -

Turns out that Jim Hansen, the outspoken NASA climatologist, didn’t attend John Marburger’s talk on Monday night, in which Marburger (who is President Bush’s science advisor), called accusations of censoring US climate scientists ‘ignorant’.

Hansen, who has long gone public with his thoughts about the problems of human-caused global warming, has said in the past that NASA public-affairs people censored his public speeches and media interviews to play down the risks of climate change. On Monday, Marburger charged that such accusations were baseless, saying that he personally had tracked down each claim and found it to be wanting. Marburger didn’t mention Hansen by name, but the subtext was clear to everyone in the audience.

Asked for his response today, Hansen simply pointed to a new book called Censoring Science: Inside the Political Attack on Dr. James Hansen and the Truth of Global Warming. (I haven’t read it and thus can’t recommend it, but here is a link so you can see at least what it looks like.) According to Hansen, it details a systematic effort to suppress climate scientists such as himself.

Asked if he had ever spoken to Marburger about the issue of censorship, Hansen said simply: “Not about this.”

Hansen isn't just confining his criticisms to US leadership, though. He's got a draft letter in the works to UK prime minister Gordon Brown and the German chancellor Angela Merkel, criticising the planned construction of coal-fired power plants in their countries.

Asked today why he was focusing on these leaders when China is constructing a coal-fired power plant at the rate of nearly one per week, Hansen said he feels that the developed world needs to take responsibility, as it has been the source of the majority of carbon dioxide emissions up until this point.

Cross-posted from Alex Witze on In the Field

Posted by Anna Barnett on December 14, 2007
Categories: AGU, Alex Witze, Conferences and Meetings | Permalink | Comments (9) | TrackBacks (0)

American Geophysical Union meeting, San Francisco -

News from the Arctic just continues to get worse. A fair number of presentations here have been dealing with the dire 2007 conditions for sea ice and the Greenland ice sheet.

First up, Greenland. Last summer, more ice melted atop Greenland than ever before measured, adding to a consistent downward trend of some 135 gigatons of ice disappearing per year. Marco Tedesco, of the Goddard Space Flight Center in Maryland, told the meeting that surface temperatures in Greenland were four to six degrees Celsius warmer than usual this summer, which helped accelerate melting, particularly at high latitudes.

The situation is even more precarious for sea ice. A couple of researchers here have been tossing around dates like 2012 or 2014 for estimates of when the Arctic might be completely ice-free in summer. While these sorts of numbers are pretty arm-waving at the moment (numbers like 2040 were previously considered to be aggressive), there’s little reason to think the situation will get better in the next couple of years. Mark Serreze, of the University of Colorado, spent a keynote lecture on Tuesday showing images of Arctic ice shrinking like a snowman left out too long in the sun. In September of this year, sea ice covered just 4.2 million square kilometers - by far the lowest record ever.

And the ice isn’t only shrinking in extent – it’s also thinning. Don Perovich, of a US army cold regions and research laboratory in New Hampshire, reported on a single but extraordinary ice buoy in the Beaufort Sea. In June the buoy measured sea ice at that location as 3.3 metres thick – “really a healthy piece of ice,” as he put it. But by the end of the summer, 70 centimetres had melted off the top – and 2.2 metres (yes, metres) off the bottom.

When you see those dramatic maps of the Arctic ice extent shrinking over time, don’t forget that it’s also thinning – a complicating factor that may just make things worse in summers to come.

Cross-posted from Alex Witze on In the Field

Posted by Anna Barnett on December 14, 2007
Categories: AGU, Alex Witze, Conferences and Meetings | Permalink | Comments (2) | TrackBacks (0)

American Geophysical Union meeting, San Francisco -

What a difference a year makes. Last AGU meeting, the evening keynote lecture was by Al Gore. This AGU, Gore was in Oslo, having picked up his Nobel Peace Prize for his climate activism, on the same day President Bush's science advisor John Marburger was giving a lecture here on climate change.

Gore got a standing ovation from the AGU scientists. Marburger got a slew of hostile questions. He probably should have expected this, given the Bush administration's policies on climate change. And lines like "scientists have lost credibility in this debate" didn't help either.

Marburger spoke for about 45 minutes on US climate policy, reinforcing many of the same messages he's put out there before. Bush recognizes the significance of climate change, Marburger argues, and has been saying as much since June 2001. The US is doing plenty to move towards taking action, including hosting a summit of major emitters in September and adopting 'aspirational' goals to improve energy consumption and develop new technologies to deal with it. Too much emphasis is being placed on mitigiation strategies for reducing carbon emissions, instead of adaptation strategies to get people to live differently in a greenhouse world.

Such messages did not go down well with the audience. Questioners pressed Marburger on mandatory emissions caps for US industries (ask Congress, says Marburger); alleged censorship of climate scientists (not a word of truth in it, he argues); and Bush's refusal to move the Kyoto protocol forward (Congress would have stymied it anyway).

Marburger also included a plea for people to read the details of the IPCC technical reports issued this year, not just the policymakers' summaries. Only in the technical reports, he argues, are the details and the complexity that everyone needs to understand in order to make informed decisions about what to do about climate change.

No one's arguing with that. But surely he hadn't forgotten that his very audience was made up of many of those who wrote the IPCC technical reports in the first place -- and they still don't agree with him.