Satellites Confirm Half-Century of West Antarctic Warming

The Antarctic Peninsula juts into the Southern Ocean, reaching farther north than any other part of the continent. The southernmost reach of global warming was believed to be limited to this narrow strip of land, while the rest of the continent was presumed to be cooling or stable.

Not so, according to a new analysis involving NASA data. In fact, the study has confirmed a trend suspected by some climate scientists.

“Everyone knows it has been warming on the Antarctic Peninsula, where there are lots of weather stations collecting data,” said Eric Steig, a climate researcher at the University of Washington in Seattle, and lead author of the study. “Our analysis told us that it is also warming in West Antarctica.”

Figure at right: Red represents areas where temperatures have increased the most during the last 50 years, particularly in West Antarctica, while dark blue represents areas with a lesser degree of warming. Temperature changes are measured in degrees Celsius. Credit: NASA/GSFC Scientific Visualization Studio > Print resolution image

The finding is the result of a novel combination of historical temperature data from ground-based weather stations and more recent data from satellites. Steig and colleagues used data from each record to fill in gaps in the other and to reconstruct a 50-year history of surface temperatures across Antarctica.

Over the years, climate research in northern latitudes led researchers to believe that the Arctic is where impacts of global climate change would be seen first. Less certain is how climate is affecting Antarctica where inland temperatures are known to plunge to -112°F, and ground-based weather stations have been sparse.

It’s this sparse data collection — from ground-stations on the Antarctic Peninsula and previous reports that much of East Antarctica has experienced cooling since 1978 — that led the International Panel on Climate Change to conclude in its most recent report that Antarctica is the one continent where we have failed to detect human-caused temperature changes.

With funding from the National Science Foundation’s Office of Polar Programs, Steig and colleagues set out to reconstruct Antarctica’s recent past. Ground-based stations have recorded temperatures since 1957, but most of those readings come from the peninsula and areas on the edges of the continent. But at the same time, scientists such as study co-author Joey Comiso of NASA’s Goddard Space Flight Center in Greenbelt, Md., have been gathering measurements from a series of Advanced Very High Resolution Radiometer (AVHRR) instruments deployed on satellites since 1981.

To construct the new 50-year temperature record, the team applied a statistical technique to estimate temperatures missing from ground-based observations. They calculated the relationship between overlapping satellite and ground-station measurements over the past 26 years. Next, they applied that correlation to ground measurements from 1957 to 1981 and calculated what the satellites would have observed.

The new analysis shows that Antarctic surface temperatures increased an average of 0.22°F (0.12°C) per decade between 1957 and 2006. That’s a rise of more than 1°F (0.5°C) in the last half century. West Antarctica warmed at a higher rate, rising 0.31°F (0.17°C) per decade. The results, published Jan. 22 in Nature, confirm earlier findings based on limited weather station data and ice cores.

While some areas of East Antarctica have been cooling in recent decades, the longer 50-year trend depicts that, on average, temperatures are rising across the continent.

Figure at right:The northern section of the Larsen B ice shelf, a large floating ice mass on the eastern side of the Antarctic Peninsula, shattered and separated from the continent on March 5, 2002, and represents a major impact that climate warming can have on the region. Credit: NASA Earth Observatory.

West Antarctica is particularly vulnerable to climate changes because its ice sheet is grounded below sea level and surrounded by floating ice shelves. If the West Antarctic ice sheet completely melted, global sea level would rise by 16 to 20 feet (5 to 6 meters).

To identify causes of the warming, the team turned to Drew Shindell of NASA’s Goddard Institute for Space Studies in New York, who has used computer models to identify mechanisms driving Antarctica’s enigmatic temperature trends.

Previously, researchers focused on Antarctic ozone depletion, which influences large-scale atmospheric fluctuations around the continent — most notably, the Southern Annular Mode, which speeds up wind flow to isolate and cool the continent.

Shindell compared Steig’s temperature data with results from a computer model that can simulate the response of the atmospheric system to changes in land surface, ice cover, sea surface temperatures, and atmospheric composition. He found the ozone-influenced Southern Annular Mode is not necessarily the primary influence on Antarctic climate. Instead, it appears that smaller-scale, regional changes in wind circulation are bringing warmer air and more moisture-laden storms to West Antarctica.

“We still believe ozone depletion can increase wind speeds around Antarctica, further isolating the interior,” Shindell said. “But it’s clear now that it’s not such a dominant influence on temperature trends.”

Reference

Steig, E.J., D.P. Schneider, S.D. Rutherford, M.E. Mann, J.C. Comiso, and D.T. Shindell, 2009: Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year. Nature, 457, 459-462, doi:10.1038/nature07669.

Latest info from NASA’s Dr. Anthony Del Genio

Separating Natural from Anthropogenic Influences in Twentieth Century Climate Data Records

Determining the human contribution to observed variations in Earth’s climate is made more difficult by the fact that the climate system also varies naturally, due to interactions of different parts of the atmosphere with each other and with the underlying oceans. These natural variations exist on time scales of several years to decades. The shorter the time span of the data record, the more difficult it is to separate systematic changes due to human activities such as greenhouse gas emissions and the production of aerosol particles from natural variations.

60S - 60N Surface Temperature Time Series

Figure 1. Changes in global surface temperature between 1900 and 2003 associated with the long-term global warming trend in two different datasets, GISTEMP and ERSST. The orange curve shows the temperature change in the GISTEMP data with all effects included. The blue dash-dot curve shows the contribution of El Niño-Southern Oscillation (ENSO) to the observed temperature fluctuations. The brown triangles show the temperature variations when the ENSO effect is subtracted from the original data. The red squares show the portion of the remaining variation that is associated with the long-term global warming trend in the GISTEMP data, and the green circles show the corresponding long-term global warming trend in the ERSST data. (Click for large GIF or PDF of figure.)

Some natural climate fluctuations like the seasonal cycle are simple to account for, since they occur on a well-known, fixed time scale. Other important natural climate influences like El Niño, the recurring warming of ocean waters in the tropical east-central Pacific Ocean, are more difficult to extract from climate datasets for two reasons. The warming does not occur at fixed time intervals, but ranges from 2-4 years. Furthermore, it can take 3-6 months for the effects in the east-central Pacific to be felt elsewhere around the globe, depending on how the circulation of the atmosphere communicates these effects to remote locations.

Scientists at the Goddard Institute for Space Studies and at the GSFC Global Modeling and Assimilation Office developed a technique to account for both the immediate effect of El Niño at its tropical Pacific source location, and its delayed effect elsewhere in the world. Once the El Niño contribution to climate variations is defined, it can be removed from a long-term climate data record, allowing longer-term climate variations to be documented. Even after this is done, some longer term natural variations remain, most notably a phenomenon called the Pacific Decadal Oscillation (PDO) that causes irregular shifts in the climate roughly every few decades. Fortunately, the spatial pattern of climate shifts due to the PDO is different from that associated with systematic human influences, and objective mathematical techniques can be used to separate them. The scientists applied this procedure to several 20th century surface temperature datasets, and also to late 20th century “reanalyses” that combine surface and satellite data with a numerical weather prediction model to produce a best estimate of variations in atmospheric temperatures and winds.

Figure 2.Spatial patterns of the long-term global warming contribution to the observed temperature trends in the GISTEMP (upper panel) and ERSST (lower panel) datasets. Orange and red colors represent warming and blue colors represent cooling over the period 1900-2003. (Click for large GIF or PDF of figure.)

The analysis shows that the leading contributor to variations in surface temperature over the 20th century is a largely systematic upward trend in most locations that appears to be consistent with estimates of the effects of increasing greenhouse gas concentrations. A few locations over land exhibit weak cooling over this time, perhaps a signature of the effects of increasing aerosol particles due to combustion and biomass burning, or a result of changes in land use. The most notable new result is the finding that the tropical Pacific has warmed significantly more slowly (and maybe not at all near the equator) than the rest of the world over this time, a feature that is not captured by most climate models simulations of 20th century climate changes. This slower warming of the tropical Pacific induces changes in the atmospheric circulation that can be seen in the reanalyses, but two different reanalysis products that incorporate different amounts of satellite data in different ways produce conflicting estimates of the change in circulation.

Aside from the long-term upward trend, the analysis captures the decadal natural fluctuations due to the PDO. A new finding that emerges from this analysis is that in addition to a well-known natural climate shift in 1976, another natural climate shift in the opposite direction apparently occurred in the mid-1990s. This latter climate shift makes it especially difficult to interpret trends seen in satellite or surface datasets that are only a decade or two in length, since an apparent upward trend in something like temperature may be partly anthropogenic and partly natural over a time period in which only one natural climate shift occurred.

Figure 3. Upper panel: Changes in global surface temperature over the period 1900-2003 associated with the Pacific Decadal Oscillation (PDO) in the GISTEMP and ERSST datasets. Middle and lower panel: Spatial patterns of surface temperature change due to the PDO in both datasets. Orange and red colors represent warming and blue colors represent cooling. (Click for large GIF or PDF of figure.)

Fortunately, by combining information about the spatial patterns of the anthropogenic and natural climate variations, it is possible to draw some conclusions. For example, an upward trend in ocean heat content from 1993-2003 has been interpreted by previous workers as a sign of anthropogenic influences that create an imbalance between the sunlight absorbed by the Earth and the heat it emits to space. At first glance the PDO shift in the mid-1990s might call such an interpretation into question. However, the spatial pattern of the PDO includes warming in some places and cooling in others; in fact, changes consistent with the PDO can be seen in the geographic pattern of observed ocean heat content changes. But in the global mean these warming and cooling changes nearly offset each other, so the overall upward trend in observed ocean heat content can only be explained by anthropogenic effects, which exhibit warming almost everywhere. On the other hand, satellite-observed changes in absorbed sunlight and emitted heat in the tropics over the period 1985-2000, which appear to have caused a strengthening of the tropical atmospheric circulation, could in principle be either anthropogenic or natural in origin.

By examining the spatial pattern of both types of climate variation, the scientists found that the anthropogenic global warming signal was relatively spatially uniform over the tropical oceans and thus would not have a large effect on the atmospheric circulation, whereas the PDO shift in the 1990s consisted of warming in the tropical west Pacific and cooling in the subtropical and east tropical Pacific, which would enhance the existing sea surface temperature difference and thus intensify the circulation. Thus, it can be concluded that the observed 15-year trend in radiative imbalance of the tropics is probably a signature of natural rather than anthropogenic climate variations.

Reference

Chen, J., A.D. Del Genio, B.E. Carlson, and M.G. Bosilovich, 2008: The spatiotemporal structure of twentieth-century climate variations in observations and reanalyses. Part I: Long-term trend. J. Climate, 21, 2611-2633, doi:10.1175/2007JCLI2011.1.

Chen, J., A.D. Del Genio, B.E. Carlson, and M.G. Bosilovich, 2008: The spatiotemporal structure of twentieth-century climate variations in observations and reanalyses. Part II: Pacific pan-decadal variability. J. Climate, 21, 2634-2650, doi:10.1175/2007JCLI2012.1.

Contact

Please address all inquiries about this research to Dr. Anthony Del Genio.

Hansen to Obama Pt II – Carbon tax with 100% dividend

In Part II, Hansen looks at policy options required to drag us out of the Sustainability Emergency. It is self-explanatory, but I thought it worth adding some notes on a cap-and-trade versus a carbon tax. Which is better?

Cap-and-Trade. Pros: (i) Cap reductions ensure falling emissions – in theory; (ii) Reduces inefficiencies or overpricing; (iii) Creates both incentives and disincentives for abatement; (iv) Chance to profit from ‘doing the right thing’. Cons: (i) Enrich middle men / brokers; (ii) Requires army of bureaucrats / new system; (iii) Encourages rent seeking – pleading by special interest groups; (iv) Limited price certainty – requires projected ‘gateways’; (5) Easy to manipulate / distort to get perverse outcomes.

Carbon Tax. Pros: (i) Clear forward price projection = investment certainty, removes incentives for hedge funds, derivatives etc., and better allows for long-term business planning; (ii) Can use current tax system; (iii) Better handles emissions intensive trade exposed industries via carbon tariffs at the trade gate; (iv) Greater societal familiarity, understanding and acceptance. Cons: (i) Politicians or bureaucrats must set costs – can introduce inefficiencies, disincentives and pressure to adjust tax rate during tough economic times; (ii) No guarantee that emissions will fall; (iii) People may still be willing to pay more for old tech because it is familiar or because they have a large historical investment in capital infrastructure or related assests.

I need to do a post about the above and expand on these points (some time!), but at least the above is a taster to see where Hansen is coming from with his carbon tax + 100% dividend idea. Many economists favour a tax over cap-and-trade (Garnaut does not) – see, for instance, the recent comments of Jeffrey Sachs when speaking at ANU.

For a critique of Hansen’s proposal by Climate Progress’ Joe Romm, see here. Romm is of course somewhat right and at the same time totally wrong. He’s right that an honest appraisal of the current situation makes it apparent that it will be extraordinarily difficult to get back to 350 ppm CO2 for centuries or millennia. We need a truly transformational, system wide change across global society to achieve that, and plenty of new tech. But he’s also downright wrong, because the corollary argument he uses is that it is therefore better to advocate for the compromise goal of 450 ppm since is more resonable and feasible. Yet even if Romm’s solution were fully achieved, it would still end in failure, because successfuly meeting the 450 ppm goal would result in utterly unacceptable climate impacts and a transformed planet. This is a common theme – flaw – among environmental advocates – failing to recognise that the laws of physics and biology don’t compromise, and have no pity.

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Tell Barack Obama the Truth – The Whole Truth (Part II of IV)

Dr James E. Hansen

Outline of policy options. The imperative of near-term termination of coal emissions (but not necessarily coal use) requires fundamental advances in energy technologies. Such advances would be needed anyhow, as fossil fuel reserves dwindle, but the climate crisis demands that they be achieved rapidly. Fortunately, actions that solve the climate problem can be designed so as to also improve energy security and restore economic well-being. A workshop held in Washington, DC on 3 November 2008 outlined options (presentations are at http://www.mediafire.com/nov3workshop — we are writing a paper, which will be available soon). The workshop focused on electrical energy, because that is the principal use of coal. Also electricity is more and more the energy carrier of choice, because it is clean, much desired in developing countries, and a likely replacement or partial replacement for oil in transportation.

The workshop topics, in order of priority, were: (1) energy efficiency, (2) renewable energies, (3) electric grid improvements, (4) nuclear power, (5) carbon capture and sequestration. Presentations are available and a summary paper is in preparation. Energy efficiency improvements have the potential to obviate the need for additional electric power in all parts of the country during the next few decades and allow retirement of some existing coal plants. Achievement of the potential of efficiency requires a combination of regulations and a carbon tax. National building codes are needed, and higher standards for appliances, especially electronics, where standby power has become a large unnecessary drain of energy. Economic incentives for utilities must be changed so that profits increase with increased energy conservation, not in proportion to amount of energy sold.

Renewable energies are gaining in economic competition with fossil fuels, but in the absence of wise policies there is the danger that declining prices for fossil fuels, and continuation of fossil fuel subsidies, could cause a major setback. The most effective and efficient way to support renewable energy is via a carbon tax (see below). The national electric grid can be made more reliable and “smarter” in a number of ways. Priority will be needed for constructing a low-loss grid from regions with plentiful renewable energy to other parts of the nation, if renewable energies are to be a replacement for coal.

Energy efficiency, renewable energies, and an improved grid deserve priority and there is a hope that they could provide all of our electric power requirements. However, the greatest threat to the planet may be the potential gap between that presumption (100% “soft” energy) and reality, with the gap filled by continued use of coal-fired power. Therefore it is important to undertake urgent focused R&D programs in both next generation nuclear power and carbon capture and sequestration. These programs could be carried out most rapidly and effectively in full cooperation with China and/or India, and other countries.

Given appropriate priority and resources, the option of secure, low-waste 4th generation nuclear power (ED: More on this in the next post, with discussion) could be available within a decade. If, by then, wind, solar, other renewables, and an improved grid prove that they are capable of handling all of our electrical energy needs, then there may be no need to construct nuclear plants in the United States. Many energy experts consider an all-renewable scenario to be implausible in the time-frame when coal emissions must be phased out, but it is not necessary to debate that matter.

However, it would be exceedingly dangerous to make the presumption today that we will soon have all-renewable electric power. Also it would be inappropriate to impose a similar presumption on China and India. Both countries project large increases in their energy needs, both countries have highly polluted atmospheres primarily due to excessive coal use, and both countries stand to suffer inordinately if global climate change continues. The entire world stands to gain if China and India have options to reduce their CO2 emissions and air pollution. Mercury emissions from their coal plants, for example, are polluting the global atmosphere and ocean and affecting the safety of foods, especially fish, on a near-global scale. And there is little hope of stabilizing climate unless China and India have low- and no-CO2 energy options.

We should also urgently pursue R&D for carbon capture and sequestration. Here too this may be done most expeditiously and effectively via cooperation with China and India. Note that, even if it is decided that coal can be left in the ground, carbon capture and sequestration with other fuels still may be needed to draw down the amount of CO2 in the air. An effective way to achieve drawdown would be to burn biofuels in power plants and capture the CO2, with the biofuels derived from agricultural or urban wastes or grown on degraded lands using little or no fossil fuel inputs.

Opponents of nuclear power and carbon capture cannot be allowed to slow these projects. No commitment for large-scale deployment of either 4th generation nuclear power or carbon capture is needed at this time. If energy efficiency and renewable energies prove sufficient for energy needs, some countries may choose to use neither nuclear power nor coal. However, we must be certain that proven options for complete phase-out of coal emissions are available within a decade.

Tax and 100% dividend. A “carbon tax with 100 percent dividend” is required for reversing the growth of atmospheric CO2. The tax, applied to oil, gas and coal at the mine or port of entry, is the fairest and most effective way to reduce emissions and transition to the post fossil fuel era. It would assure that unconventional fossil fuels, such as tar shale and tar sands, stay in the ground, unless an economic method of capturing the CO2 is developed.

The entire tax should be returned to the public, equal shares on a per capita basis (half shares for children up to a maximum of two child-shares per family), deposited monthly in bank accounts. No bureaucracy is needed.

A tax should be called a tax. The public can understand this and will accept a tax if it is clearly explained and if 100 percent of the money is returned to the public. Not one dime should go to Washington for politicians to pick winners. No lobbyists need be employed. The public will take steps to reduce their emissions because they will continually be reminded of the matter by the monthly dividend and by rising fossil fuel costs. It must be clearly explained to the public that the tax rate will continue to increase in the future. When fuel prices decline, the tax should increase, to retain the incentive for transitioning to the post-fossil-fuel-era. The effect of reduced fossil fuel demand will be lower fossil fuel prices, making the tax a larger and larger portion of energy costs (for fossil fuels only). Thus the country will stop hemorrhaging its wealth to oil-producing states.

Tax and dividend is progressive. A person with several large cars and a large house will have a tax greatly exceeding the dividend. A family reducing its carbon footprint to less than average will make money. Everyone will have an incentive to reduce their carbon footprint. The dividend will stimulate the economy, spur innovation, and provide money that allows people to purchase low carbon products.

A carbon tax is honest, clear and effective. It will increase energy prices, but low and middle income people, especially, will find ways to reduce carbon emissions so as to come out ahead. The rate of infrastructure replacement, thus economic activity, can be modulated by how fast the carbon tax rate increases. Effects will permeate society. Food requiring lots of carbon emissions to produce and transport will become more expensive and vice versa, encouraging support of nearby farms as opposed to imports from half way around the world. Beware of alternative approaches, such as ‘percent emission reduction goals’ and ‘cap and trade’. These are subterfuges designed to allow business-as-usual to continue, under a pretense of action, a greenwashing. Hordes of lobbyists will argue for these approaches, which assure their continued employment. The ineffectiveness of ‘goals’ and ‘caps’ is made blatantly obvious by the fact that the countries promoting them are planning to build more coal-fired power plants.

If the United States accedes to the ineffectual ‘goals’ and ‘caps’ approach, in effect continuation of the Kyoto Protocol approach, it will practically guarantee disastrous climate change. Instead it should persuasively argue that other countries also adopt tax and dividend. The countries agreeing to this approach will also agree that imports from a country that does not apply a comparable carbon tax will be taxed at the port of entry. That tax, which should be added to the public’s dividend, will be a strong incentive for all countries to participate.

A carbon tax is necessary but not sufficient. By itself a carbon tax cannot solve the energy problem and allow rapid coal phase-out. There also must be better efficiency standards in building codes, for vehicles, and in appliances and electronics. Profit incentives for utilities must be changed, so as to encourage efficiency as opposed to selling as much energy as possible. These are only examples of the many things to be done. But all of these things will be done easier and more effectively in the presence of a carbon tax. Indeed, a carbon tax is essential. It is the tool that will impact people’s decisions and lifestyle choices for the short-term, middle-term and long-term, allowing the world to move as gracefully as possible to the post-fossil-fuel-era. In this way we will leave in the ground the hardest to extract fossil fuels as we move rapidly to clean energy sources of the future.

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Part III will talk about Nuclear Power – a very important topic and worth a bit of background comments by myself. So I haven’t dwelt on it in my preamble to this post.

Hansen to Obama Pt 1 – the Now or Never plan

It would be an understatement of epic proportions to say that President-elect Barack Obama has a big job ahead of him come January 2009. Plenty of people will be giving him ‘advice’ – some good, most not (if the history of vested interests twisting the political process over the last few decades is any guide).

Scientists have something particularly important to communicate to Obama on climate change and energy. It’s based on hard-won, peer-reviewed evidence – not spin and denial – and it’s a super urgent message. In broad terms, it’s the policy implications of the Sustainability Emergency.

One of the most respected climate change scientists, Dr James Hansen of NASA, has drafted a statement which Obama should definitely read. I think BraveNewClimate readers should study it too. It is perhaps the single best succinct summary of the problems and solutions of global warming and related issues that I’ve read.

As such, I’ve decided to republish it in full over the next week, and invite feedback from readers. As Jim says, “This is a first draft. Criticisms would be much appreciated.” I’ll make sure he gets to see them. To access the original PDF, click here. Or wait and follow it here. I’ve enhanced the original slightly by adding some judicious hyperlinks, which will allow readers to explore these ideas further.

First up, it’s an overview of the core problem – the threats of inaction (or weak progress), the urgency of the problem and the fallacy of part-solutions, and the principle implication – coal emissions must stop ASAP.

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Tell Barack Obama the Truth – The Whole Truth (Part I of IV)

Dr James E. Hansen

Embers of election night elation will glow longer than any prior election. Glowing even in other nations, and for good reason. We are all tied together, more than ever, like it or not. Barack Obama’s measured words on election night, including eloquent recognition of historic progress, from the viewpoint of a 106-year-old lady, still stoke the embers. But he was already focusing on tasks ahead, without celebratory excess. Well he should.

The challenge he faces is unprecedented. I refer not to the inherited economic morass, as threatening as it is. The human toll due to past failures and excesses may prove to be great, yet economic recessions, even depressions, come and go. Now our planet itself is in peril. Not simply the Earth, but the fate of all its species, including humanity. The situation calls not for hand-wringing, but rather informed action.

Optimism is fueled by expectation that decisions will be guided by reason and evidence, not ideology. The danger is that special interests will dilute and torque government policies, causing the climate to pass tipping points, with grave consequences for all life on the planet. The President-elect himself needs to be well-informed about the climate problem and its relation to energy needs and economic policies. He cannot rely on political systems to bring him solutions – the political systems provide too many opportunities for special interests.

Here is a message I think should be delivered to Barack Obama. This is a first draft. Criticisms would be much appreciated.

Climate threat. The world’s temperature has increased about 1°F over the past few decades, about 2°F over land areas. Further warming is “in the pipeline” due to gases already in the air (because of climate system inertia) and inevitable additional fossil fuel emissions (because of energy system inertia). Although global warming to date is smaller than day-to-day weather fluctuations, it has brought global temperature back to approximately the highest level of the Holocene, the past 10,000 years, the period during which civilization developed. Effects already evident include:

1. Mountain glaciers are receding worldwide and will be gone within 50 years if CO2 emissions continue to increase. This threatens the fresh water supply for billions of people, as rivers arising in the Himalayas, Andes and Rocky Mountains will begin to run dry in the summer and fall.

2. Coral reefs, home to a quarter of biological species in the ocean, could be destroyed by rising temperature and ocean acidification due to increasing CO2.

3. Dry subtropics are expanding poleward with warming, affecting the southern United States, the Mediterranean region, and Australia, with increasing drought and fires.

4. Arctic sea ice will disappear entirely in the summer, if CO2 continues to increase, with devastating effects on wildlife and indigenous people.

5. Intensity of hydrologic extremes, heavy rains, storms and floods on the one hand, and droughts and fires on the other, are increasing.

Some people say we must learn to live with these effects, because it is an almost godgiven fact that we must burn all fossil fuels. But now we understand, from the history of the Earth, that there would be two monstrous consequences of releasing the CO2 from all of the oil, gas and coal, consequences of an enormity that cannot be accepted. One effect would be extermination of a large fraction of the species on the planet. The other is initiation of ice sheet disintegration and sea level rise, out of humanity’s control, eventually eliminating coastal cities and historical sites, creating havoc, hundreds of millions of refugees, and impoverishing nations.

Species extermination and ice sheet disintegration are both ‘non-linear’ problems with ‘tipping points’. If the process proceeds too far, amplifying feedbacks push the system dynamics to proceed without further human forcing. For example, species are interdependent – if a sufficient number are eliminated, ecosystems collapse. In the physical climate system, amplifying feedbacks include increased absorption of sunlight as sea and land ice areas are reduced and release of methane, a powerful greenhouse gas, as permafrost melts.

The Earth’s history reveals examples of such non-linear collapses. Eventually, over tens and hundreds of thousands of years, new species develop, and ice sheets return. But we will leave a devastated impoverished planet for all generations of humanity that we can imagine, if we are so foolish as to allow the climate tipping points to be passed.

Urgency. Recent evidence reveals a situation more urgent than had been expected, even by those who were most attuned. The evidence is based on improving knowledge of Earth’s history – how the climate responded to past changes of atmospheric composition – and on observations of how the Earth is responding now to human-made atmospheric changes. The conclusion – at first startling, but in retrospect obvious – is that the human-made increase of atmospheric carbon dioxide (CO2), from the pre-industrial 280 parts per million (ppm) to today’s 385 ppm, has already raised the CO2 amount into the dangerous range. It will be necessary to take actions that return CO2 to a level of at most 350 ppm, but probably less, if we are to avert disastrous pressures on fellow species and large sea level rise.

The good news is that such a result is still possible, if actions are prompt. Prompt action will do more than prevent irreversible extinctions and ice sheet disintegration: it can avert or reverse consequences that had begun to seem inevitable, including loss of Arctic ice, ocean acidification, expansion of the subtropics, increased intensity of droughts, floods, and storms.

Principal implication. CO2 is not the only human-made gas that contributes to global warming, but it is the dominant gas and it has the longest lifetime. Much of the CO2 increase caused by burning fossil fuels remains in the air more than 1000 years. So CO2 must be the focus of efforts to stop human-caused climate change.

It would be easy to jump to the conclusion that solution of global warming is to phase down total fossil fuel emissions by some specified percentage. That approach will not work as a strategy. The reason for that conclusion and an outline of a better strategic approach follow immediately from geophysical boundary constraints.

are provided in the published paper.”]

Figure 1. (a) Fossil fuel and net land-use CO2 emissions (purple), and potential fossil fuel emissions (light blue). Fossil fuel reserve estimates of EIA, IPCC and WEC differ as shown. (b) Atmospheric CO2 if coal emissions are phased out linearly between 2010 and 2030, calculated using a version of the Bern carbon cycle model. References [EIA (Energy Information Administration), IPCC (Intergovernmental Panel on Climate Change), and WEC (World Energy Council)

Figure 1a shows oil, gas and coal reserves, with the purple portion being the amount that has already been burned and emitted into the atmosphere. Despite uncertainty in the magnitude of undiscovered reserves, their amounts are certainly enough to yield atmospheric CO2 greater than 500 ppm. That amount would be disastrous, assuring unstable ice sheets, rising sea level out of humanity’s control, extermination of a large fraction of the species on Earth, and severe exacerbation of climate impacts discussed above.

Oil is used primarily in vehicles, where it is impractical to capture CO2 emerging from tailpipes. The large pools of oil remaining in the ground are spread among many countries. The United States, which once had some of the large pools, has already exploited its largest recoverable reserves. Given this fact, it is unrealistic to think that Russia and Middle East countries will decide to leave their oil in the ground. A carbon cap that slows emissions of CO2 does not help, because of the long lifetime of atmospheric CO2. In fact, the cap exacerbates the problem if it allows coal emissions to continue. The only solution is to target a (large) portion of the fossil fuel reserves to be left in the ground or used in a way such that the CO2 can be captured and safely sequestered.

Coal is the obvious target. Figure 1b shows that if there were a prompt moratorium on construction of new coal plants, and if existing ones were phased out linearly over the period 2010-2030, then atmospheric CO2 would peak during the next few decades at an amount somewhere between 400 and 425 ppm. The peak value depends upon whose estimate of undiscovered reserves is more accurate. It also depends upon whether oil in the most extreme environments is exploited or left in the ground, and thus it depends on the carbon tax (see next post).

This coal-phase-out scenario yields the possibility of stabilizing climate. Overshoot of the safe CO2 level is sufficiently small that improved agricultural and forestry practices, including reforestation of marginal lands, could bring CO2 back below 350 ppm, perhaps by the middle of the century. But if construction of new coal plants continues for even another decade it is difficult to conceive a practical, natural way to return CO2 below 350 ppm.

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Part II of IV will focus on policy options…

Interview with Prof Stephen Schneider

As part of a recent textbook I wrote with Prof Navjot Sodhi and Assoc Prof Corey Bradshaw (Tropical Conservation Biology, Wiley-Blackwell, 2007), we interviewed some well known scientists for a ‘Spotlight’ series. Other interviews have been published on BNC’s sister blog, ConservationBytes.

For the chapter entitled “Climate Change: Turning up the tropical heat“, we put some questions to Prof Stephen Schneider. Steve is a good friend of mine who I first met at an extinction conference in Okazaki, Japan, in 2004 – the same conference, incidentally, that motivated Tim Flannery to write The Weather Makers). Steve was later a Thinker in Residence in Adelaide and produced an important public policy document for South Australia on government actions to combat climate change. We’ve also done a tag-team interview on carbon trading.

Anyway, here is the interview, the format for which includes a small biography, a list of major scientific publications and a Q & A on the person’s particular area of expertise.

Biography

I am the Melvin and Joan Lane Professor for Interdisciplinary Environmental Studies, Professor of Biological Sciences, and Professor by Courtesy of Civil and Environmental Engineering at Stanford University. I am Co-Director of the Center for Environmental Science and Policy in the Freeman-Spogli Institute and a Senior Fellow in the Woods Institute for the Environment. I received my PhD in Mechanical Engineering and Plasma Physics from Columbia University, USA, in 1971. When considering research areas then, I became aware that anthropogenic dust can cool the climate and greenhouse gases can warm it, and thus decided to switch to studying climate science. Today, my global change interests include the ecological and economic implications of climatic change; integrated assessment of global change; climatic modeling of paleoclimates and human impacts on climate (e.g., carbon dioxide “greenhouse effect”); dangerous anthropogenic interference with the climate system; food/climate and other environmental science/public policy issues; and environmental consequences of nuclear war. I am also dedicated to advancing environmental literacy in all levels of education.

I co-founded the Climate Project at NCAR in 1972 and founded the interdisciplinary journal, Climatic Change, in 1975, which I continue to edit today. I was honoured in 1992 with a MacArthur Fellowship for my ability to integrate and interpret the results of global climate research through public lectures, seminars, classroom teaching, environmental assessment committees, media appearances, Congressional testimonies, and research collaboration with colleagues. I was elected to membership in the US National Academy of Sciences in 2002, and received both the National Conservation Achievement Award from the National Wildlife Federation and the Edward T. Law Roe Award from the Society of Conservation Biology in 2003, and the Banksia Foundation’s International Environmental Award in Australia in 2006. I have served as a Coordinating Lead Author in Working Group II of the Intergovernmental Panel on Climate Change (IPCC) from 1997 to the present. My recent work has centered on the identification and classification of ‘key vulnerabilities’ in the climate system and the role of risk management in climate policy decision-making. I continue to serve as an advisor to decision-makers and stakeholders in industry, government, and the nonprofit sectors. I am also engaged in improving public understanding of science and the environment through extensive media communication and public outreach.

5 most-relevant publications:

Schneider, S.H. and M.D. Mastrandrea, 2005:  “Probabilistic assessment of ‘dangerous’ climate change and emissions pathways,” Proceedings of the National Academy of Sciences 102, 15728-15735.

Root, Terry L., Dena MacMynowski, Michael D. Mastrandrea, and Stephen H. Schneider, 2005: “Human-modified temperatures induce species changes: Joint attribution,” Proceedings of the National Academy of Sciences, 102, 7465-7469.

Mastrandrea, M.D. and S.H. Schneider, 2004: “Probabilistic Integrated Assessment of: ‘Dangerous’ Climate Change,” Science 304, 571–575.

Schneider, S.H., and K. Kuntz-Duriseti, 2002: “Uncertainty and Climate Change Policy,” Chapter 2, in Schneider, S.H., A. Rosencranz, and J.-O. Niles, (eds.) Climate Change Policy: A Survey, Washington D.C.: Island Press, 53–88.

Schneider, S.H., 1990: Global Warming, Are We Entering the Greenhouse Century? Cambridge: The Lutterworth Press, 343 pp. (Japanese edition: Diamond, Tokyo; U.K. edition: Lutterworth, Cambridge; Italian edition: Armenia Editore, Milano; Paperback version (1990): New York: Vintage Books, New York, 343 pp.

Questions & Answers:

1. Climate has varied throughout earth’s history. Why is contemporary climate change particularly dangerous to biodiversity?

The current, much-faster-than-natural rate of temperature change, coupled with multiple stressors, makes contemporary climate change particularly threatening to biodiversity. The forecasted global average rate of temperature increase over this century (approximately 1–5oC/century) greatly exceeds by a rough order of magnitude rates typically sustained during the last 20,000 years. The balance of evidence from meta-analyses of species from many different taxa examined at disparate locations around the globe suggests that a significant impact from recent climatic warming is discernible in the form of long-term, large-scale alteration of animal and plant populations. This evidence takes the form of poleward or upward range shifts and changes in phenology such as dates of migration, breeding and flowering (making spring events for some species 10–15 days earlier over the past few decades). The IPCC has extended climate impact analyses to include such ‘environmental systems’ as sea- and lake-ice cover and mountain glaciers. Clearly, if such climatic and ecological signals are now being detected above the background of climatic and ecological noise for a twentieth-century warming of ‘only’ 0.6oC, it is likely that the combination of highly disturbed landscapes and temperature increases up to an order of magnitude larger by 2100 will have a dramatic impact on biodiversity and ecosystem functioning.

2. Will climate change have less impact in the tropics than at higher latitudes?

There are already signs of severe stress in high-latitude and alpine habitats and in coral reefs, showing that these ecosystems are experiencing significant impacts at present levels of climate change. Human-mediated climate change is or is projected to be affecting tropical biotas via range shifts (latitudinal and elevational), changes in phenology, increasing prevalence, distribution and severity of diseases and parasites, coral bleaching, drying of freshwater systems and sea level rise. The magnitude of temperature changes will be less in the tropics, but changes in the hydrological cycle may still be large. Some models suggest that above a few degrees more warming, tropical forests will switch from a sink to a source of CO2 emissions—a dramatic change if it were to occur as projected. The potential for forest fires under such conditions could become a major threat to forests both in Amazonia and in Southeast Asia because the forests in these regions are not adapted to fire. Species living at higher altitudes in the tropics are particularly vulnerable to climate change due to the disruption or loss of specific microclimates and the higher likelihood of invasive species influx from lower elevations.

3. How might climate change interact with other threats to tropical biodiversity, such as invasive species, fire, and land clearance for agriculture?

Adverse impacts on biodiversity caused by a synergistic suite of threats are already occurring and will continue to intensify climate impacts. It is expected that further warming could substantially rearrange the ranges and interactions of many species. However, because of human land uses such as agriculture, urban settlement and roads, most species no longer have a free range in responding (e.g. by freely migrating) to climatic shifts. The synergism or combined complex interactions of effects among climate changes, land use disturbances, the introduction of exotic species and artificial chemicals will most likely collectively impact on wildlife and terrestrial systems much more significantly than if each of these disturbances were simply considered separately.

4. Are there any benefits of a warmer world rich in atmospheric carbon for tropical ecosystems?

Undoubtedly some species—particularly those that are adaptable, such as crows or weeds—can flourish in disturbed conditions better than specialists such as warblers or orchids. Thus, although the populations of some well-adapted generalists may well expand, the slow rate of speciation and the major threat of endangerment to more vulnerable species have resulted in estimates of 10–50% of species becoming extinct in the next two centuries if warming of more than a few degrees occurs.

5. Based on current trends, how long will it be before the earth’s climate crosses an irreversible and potentially catastrophic tipping point?

It is very difficult to define precise tipping points given remaining uncertainties. Nevertheless, there are potential thresholds for events like ice sheet disintegration or coral reef bleaching, although most such estimates appear as ranges—for example, 1–3oC warming for major reef damages and 1.5–4oC warming for major ice sheet disintegrations.   The bottom line is that the harder and faster the system is disturbed, the more likely such catastrophic changes become.

(with thanks to Navjot Sodhi, Corey Bradshaw, Ward Cooper, Wiley-Blackwell and Stephen Schneider for permission to reproduce the text – buy your copy of Tropical Conservation Biology here)