29 September 2010

Geoengineering Today

Geoengineering . . . You're Looking At It

[crossposted from Doc's Green Blog]

"Geoengineering" refers to large-scale efforts to manipulate the climate. There are several current and recent activities that have been undertaken for other purposes, but which have the effect of changing climate, for good or ill.

We will set aside the deliberate release of 25 billion tonnes of greenhouse gases from combustion of fossil fuels each year, a geoengineering "experiment" that seems already to be creating many interesting effects. Although this is one of the largest geoengineering projects ever undertaken, it has been discussed in some detail elsewhere.

The three current geoengineering programs this post will consider are:
  • China's "Great Green Wall"
  • Large-scale expansion of irrigation
  • Large-scale deforestation

Afforestation Changes The Climate

Since 1978 China has been engaged in a vast project that has been called the "Great Green Wall". In 1981 the National People’s Congress passed a resolution to require every citizen above age 11 to plant at least three Poplar, Eucalyptus, Larch or other saplings every year. [Source] Afforestation has already covered 500,000 square kilometres with new artificial forest, and China hopes to have such forests on 400 million hectares--more than 42% of its land area--by 2050.

Chinese Vice Premier Hui Liangyu recently called for even greater efforts to increase China's forest cover.

The immediate goal of this program is to slow the encroachment of desert from the north and west into areas formerly grassland. Whether artificial forests can do this remains to be seen. And there are some concerns about other effects, such as increased water use. [More at Wikipedia.] A similar effort was the shelterbelt program in the U.S. Great Plains in the 1930s, but that was not on a Chinese scale.

Since forests affect the water cycle, albedo, and cloud cover of an area they can be expected to modify the local climate, and perhaps the climate downwind.

Irrigation Changes The Climate

Large programs of crop irrigation in Asia and North America result in large quantities of water evaporating from fields and water channels, and by transpiration through plants.

Because of the latent heat of water, more evaporation means more cooling in some places, and more rain means more warming in other places. (What is latent heat? See this post at Science In Action.)  A recent article in the Journal of Geophysical Research (pdf here, New York Times Green blog post about it here) says irrigation may be causing cooling in some regions, locally masking the effects of global warming.

The model runs reported in this paper suggest that parts of northern India may have experienced several degrees of cooling due to all the heat absorbed by irrigation water applied to crops in the later part of the 20th century. Weather patterns may even have been affected enough to reduce the amount of rain in the Bay of Bengal branch of the Southwest Monsoon. (Other researchers got somewhat different or even contradictory results with different models.)

This is a bit scary because if groundwater depletion leads to reduction in irrigation in the future, the resulting reduction of cooling effect could have both local an regional climate effects, including sharply higher temperatures and changes in rainfall amounts and distribution.

Deforestation Changes The Climate

Large-scale deforestation for conversion of forest to pasture or cropland is an old story.  Such deforestation took place over much of Europe and temperate North America in earlier centuries. A similar massive land-use change was the breaking up of the American prairie grasslands for farming in the 19th century.

When forests are burned (the usual method) to clear them for agriculture the carbon trapped in the trees is dumped into the atmosphere. Soot and other particulates are also released in great quantities. Both CO2 and black carbon have significant local and global effects on climate.

The Nature Conservancy says "deforestation and land use change contributes approximately 20 to 25 percent of the carbon emissions that cause climate change." This Wikipedia article on per-capita greenhouse gas emissions by country, which uses data from the World Resources Institute for 2000, suggests land-use changes account for about 17% of greenhouse gas emissions.

So land-use changes, mostly deforestation, annually release about the same amount of greenhouse gases as the USA or China does from all burning of fossil fuels.

The Future of Geoengineering

Several enormous geoengineering projects have been discussed as ways to undo some of the damage the earlier geoengineering projects mentioned above are causing. This previous post looks at some of the limitations and potential impacts of such schemes. Whether such consequences are "unintended", "unavoidable", or "somebody else's problem" will be part of the discussion of these projects in years to come.

14 September 2010

Storms of My Grandchildren--James Hansen

Serious Science for Critical Times

Storms of My Grandchildren cover image
[Crossposted from Doc's Green Blog.]

Dr. James Hansen has written a personal, idiosyncratic, urgent, heartfelt book about climate change, past and future. The reader can feel his frustration at the stubborn inaction of governments in the face of what he sees as a looming disaster. But one also feels the warmth, the grandfatherliness, advertised by the book's title. Storms of My Grandchildren: The Truth About the Coming Climate Catastrophe and Our Last Chance to Save Humanity is more than half science, but it is part emotion. Scientists are people too.

The book's message in brief: It's worse than we thought, and here's why. Politicians are subservient to fossil fuel polluters. We have to do something about it unless we want to leave our descendants a severely damaged, and perhaps uninhabitable, world.

Hansen, in spite of the public role he has felt called upon to play, is 100% scientist. The book's structure uses his own journey as a researcher, and as an expert called upon to brief government leaders, to explain a lot of serious science. Climate forcings, paleoclimatology, aerosols, and more are presented to the reader in more depth than is usual for a book targeted at the general public.

Science of Climate Change

graph from Fig. 18
Color version of book's Figure 18
"Deep ocean temperature during the Cenozoic era"
[Do we really want to go back to the
Permian-Eocene Thermal Maximum
when sea levels were 75 meters higher?]
Some readers will be tempted to skip over some of the technical background. They will miss a fascinating part of the message. The scientific explanations are clear enough, although Dr. Hansen does take some shortcuts and requires the reader to pay attention. He has been immersed in this field for nearly 50 years and is used to its jargon, units and arguments. On the other hand this is not meant to be a textbook. Some compression and ellipsis is unavoidable. Readers who glide over the technical parts will be missing something important.

The science, Hansen is saying, is fundamental, undeniable, and convincing. He naturally feels that the reader should understand it in order to follow the argument that climate change is a serious threat to society. We may be setting in motion changes in the Earth's climate that could wipe out life on the planet and will certainly make life tougher for coming generations in this century. He urgently wants to get that message across.

Frustration with Inaction

This is a polemic. Hansen feels that politicians are in the palm of economic interests that benefit from continuing "business as usual" even in the face of urgent warnings of enormous risks. He is urging the people to take action.

His deep understanding of climate forcings and their effects in the past leads him to a much greater degree of alarm than many other scientists or environmentalists feel comfortable expressing. He has been criticized by other climate activists for lacking "a realistic idea of what is politically possible".

Hansen doesn't pull his punches. He thinks "cap and trade" is useless. He thinks expanded use of nuclear power is part of the solution. In these areas he treads beyond the strict boundaries of his expertise.

But when he says that targets like 450ppm of CO2 in the atmosphere are much too high and will lead to disaster, he speaks of science he has studied in depth. He implores us to get back to 350ppm.
A striking conclusion from this analysis is the value of carbon dioxide--only 450 ppm, with estimated uncertainty of 100 ppm--at which the transition occurs from no large ice sheets to a glaciated Antarctica. This has a clear, strong implication for what constitutes a dangerous level of atmospheric carbon dioxide. If humanity burns most of the fossil fuels, doubling or tripling the preindustrial carbon dioxide level, Earth will surely head toward the ice-free condition, with sea level 75 meters (250 feet) higher than today. It is difficult to say how long it will take for the melting to be complete, but once ice sheet disintegration gets well under way, it will be impossible to stop.

With carbon dioxide the dominant climate forcing, as it is today, it obviously would be exceedingly foolish and dangerous to allow carbon dioxide to approach 450 ppm. [p. 160]
Neither politicians nor political climate activists and thought leaders like to be told that they are being "exceedingly foolish". Yet Hansen goes further. "But maybe Congress doesn't really care about your grandchildren. [p. 215]"  "The present situation is analogous to that faced by Lincoln with slavery and Churchill with Nazism--the time for compromises and appeasement is over. [p. 211]"

A Book Worth Reading

Sophie and Connor,
Dr. Hansen's grandchildren
Dr. Hansen has decided that he knows something important, and that he must speak out about it. Not everyone will agree with the urgent, even intolerant, tone of his call to action. But it is based on true feelings founded on decades of serious science.

How the book's call to action affects you will depend on your biases and personality. Some will be moved to do something, some will be more informed but still passive, some will be annoyed, some will be indifferent. But all will have learned something.

The science that is at the heart of the book is worth seriously considering. If Hansen is right, our children, grandchildren and more distant heirs are going to curse us. We heard the message, and we are doing little or nothing. We blunder past tipping points with little concern for those who will have to live in the world we are leaving them.

Want to buy it? Click here: Storms of My Grandchildren: The Truth About the Coming Climate Catastrophe and Our Last Chance to Save Humanity

Dr. Hansen's web site is here.

He and Dr. Makiko Sato have also created the Updating the Climate Science page to supplement and update the content of Storms of my Grandchildren.

The book's official web page is here.

Good reviews of the book at Daily Kos and the Los Angeles Times.

The color version of the book's Figure 18 is from this site.

The picture of Sophie and Connor is from here. A black-and-white version is in the book at page 272.

The contents of the book are copyright © 2009 by James Hansen. The illustrations are copyright © 2009 by Mikiko Sato.

07 September 2010

Geoengineering No Simple Solution

Can we use geoengineering to avoid the worst effects of climate change caused by increasing atmospheric carbon dioxide? Don't count on it, say two recent scientific articles.

Sea Level Rise Can't Be Halted By Geoengineering

Researchers from China/Finland, the UK and Denmark modeled the effect of various geoengineering ideas on sea level rise. Their paper "Efficacy of geoengineering to limit 21st century sea-level rise" appears in the Proceedings of the National Academy of Sciences (abstract and access here). (They deserve thanks for making their paper open access.)

They find "sea-level rise by 2100 will likely be 30 cm higher than 2000 levels despite all but the most aggressive geoengineering under all except the most stringent greenhouse gas emissions scenarios." This means that even if we spend trillions on vast projects, and even if those projects work as planned, unless we also adopt tough measures to cut emissions sea level still goes up a foot.

And they say "Loss of low-lying land, combined with asset exposure to urban flooding due to the combined effects of climate change (sea-level rise and increased storminess), may reach 10% of projected global gross world product (GWP) in the 2070’s."

There are two things to consider when digesting that statement:
  • The authors are only talking about a meter of sea level rise in this century, at the lower end of current projections, and
  • The current recession cut the global economy by less than 2% from what it might have been without the recession. Imagine 10%.
They modeled several proposed projects:
  • Giant mirrors in space--These reduce climate forcing from the Sun's radiation, but leave greenhouse gases in the atmosphere where they continue to have their other negative effects such as ocean acidification. Also this project would be enormously expensive.
    • Who could think that launching 20 million tonnes of mirrors into space could be less of a blow to the economy than cutting greenhouse gas emissions by reducing coal use? 
    • For comparison, the International Space Station weighs only 370,000 tonnes, and it has taken a decade to get it up there. It is the most expensive object ever constructed. It has been estimated to cost €100 billion over its 30-year life. Could taxpayers afford €5 trillion?
  •  Aggressive afforestation, replanting cut forests and planting trees to create new forests, might be able to take some CO2 out of the atmosphere, reducing that climate forcing. But CO2 could only be reduced by about 45ppm. Humans have put more than a hundred ppm of CO2 into the atmosphere over the past century or so, and are adding about 2ppm per year. So models still showed significant sea level rise.
  • Increasing biochar levels in the soil would reduce the CO2 levels by even less--about 35ppm.
  • Aggressive conversion from petroleum and coal to biofuels with capture and storage of the resulting CO2 from their combustion could reduce atmospheric CO2 180ppm by 2100.
  • A combination of afforestation, biochar sequestration and biofuels with carbon capture and storage could take 250ppm of CO2 out of the atmosphere and might keep sea level rise to "only" 20 to 40 cm.
  • Injecting SO2 into the atmosphere, equivalent to a major volcanic eruption every year and a half, could reduce global temperature rise a degree or so, but would leave the CO2 in the atmosphere. Such a project might reduce sea level rise by 20cm or so. And if the program were ever ended warming would bounce back in a short time, with accompanying sea level rise.
    • And see the other findings below for more problems with SO2 injection.
In the end they conclude "Substituting geoengineering for greenhouse gas emission abatement or removal constitutes a conscious risk transfer to future generations."

Geoengineering Helps Some But Hurts Others

Researchers from Carnegie Mellon and Oxford studied the regional impacts of various geoengineering concepts. Their work is reported in Nature Geoscience. (Abstract only here. Unfortunately these researchers did not make their findings open access.)

They modeled solar-radiation management by adding reflecting aerosols to the stratosphere. Previous modeling studies suggested that such an approach could stabilize global temperatures and reduce global precipitation. Their findings:
Our results confirm that solar-radiation management would generally lead to less extreme temperature and precipitation anomalies, compared with unmitigated greenhouse gas emissions. However, they also illustrate that it is physically not feasible to stabilize global precipitation and temperature simultaneously as long as atmospheric greenhouse gas concentrations continue to rise. Over time, simulated temperature and precipitation in large regions such as China and India vary significantly with different trajectories for solar-radiation management, and they diverge from historical baselines in different directions. Hence, it may not be possible to stabilize the climate in all regions simultaneously using solar-radiation management. Regional diversity in the response to different levels of solar-radiation management could make consensus about the optimal level of geoengineering difficult, if not impossible, to achieve.
So shooting millions of tonnes of SO2 into the stratosphere can cool the globe, but its effects are uneven. An article in The Economist provides more details:
A particularly salient example of this comes from Asia. There were a number of geoengineering scenarios in which the climate in both India and China in the 2020s looked quite like that of the 1990s, though in all geoengineering scenarios using this particular model India gets a bit wetter than it was before and in most of them China gets a bit drier. Go out to the 2070s, though, and the geoengineering scenarios strong enough to keep China’s temperature 1990s-ish cool India below its baseline temperature, while weaker scenarios that keep India’s temperature at the levels of the 1990s see China heat up.
That said, in both cases all the geoengineering options gave results for both temperature and precipitation closer to 1990s levels than the models projected for a world without geoengineering. In this sense both countries were "winners"—but maximising the benefits for one would still come at the expense of the other. The same lesson seems to apply quite generally across the world. Few if any regions stand out as certain losers from geoengineering if you accept that it is worth trading off a large change in temperature for a smaller drop in precipitation (in terms of change on the levels seen before the geoengineering). But different levels of geoengineering seem optimal for different regions.
So the question would be, who gets to decide what geoengineering to do? Presumably those who pay for it will control which projects get done. And naturally they will undertake projects that benefit themselves, even if they cause harm elsewhere in the world. This would be geopolitically very unfriendly, sort of like declaring war.

If these results hold I doubt we will see much geoengineering until and unless climate change gets so disruptive that the community of nations falls apart and its every one for itself.

A Scientific American blog post also covered the sea level rise story.

02 September 2010

Plants Unhappy About Global Warming

Rice field in Bangladesh
New science raises serious concerns about the negative impact of global warming on crop yields and plant productivity in general.

This could be one of the most severe social and economic effects of climate change.

Rice Yields Hurt By Warming

Researchers from the University of California, Duke, National Bureau of Economic Research, IRRI and FAO published a very revealing paper in PNAS. They studied 227 intensively managed irrigated rice farms in six important rice-producing countries over several years. Their findings "imply a net negative impact on yield from moderate warming in coming decades. Beyond that, the impact would likely become more negative, because prior research indicates that the impact of maximum temperature becomes negative at higher levels." Rising temperatures, especially nighttime temperatures, will hurt rice yields.

The paper is behind a pay wall, but there is a good BBC News article on their results. It says they "found that over the last 25 years, the growth in yields has fallen by 10-20% in some locations, as night-time temperatures have risen. ... Although yields have risen as farming methods improved, the rate of growth has slowed as nights have grown warmer." And "if temperatures continue to rise as computer models of climate project, Mr Welch says hotter days will eventually begin to bring yields down."

The question is whether rice improvement efforts (plant breeding) can get ahead of the negative effects of rising temperatures.

This EurekAlert release summarizes the results.

Net Plant Primary Production Down

Researchers at the University of Montana studied terrestrial net primary production. Net primary production (NPP) is the total net fixation of carbon by photosynthesis in an ecosystem. They found that "Large-scale droughts have reduced regional NPP, and a drying trend in the Southern Hemisphere has decreased NPP in that area, counteracting the increased NPP over the Northern Hemisphere."

These results were surprising since earlier studies had shown increasing plant carbon capture with rising temperatures in the 80s and 90s. However temperatures since 2000 have been the highest in modern records and accompanying droughts have apparently cut into global plant growth.

Again the Science article is not open access, but this EurekAlert release has some more information on the results and their implications.

While longer growing seasons and higher atmospheric carbon dioxide levels may favor more carbon fixation in some northerly regions, more of the globe is water-limited and more drought could hurt total carbon fixation more than warming trends would boost it. As the authors say in their abstract, "A continued decline in NPP would not only weaken the terrestrial carbon sink, but it would also intensify future competition between food demand and proposed biofuel production."

Plankton Declining With Warming Seas

Researchers from Dalhousie University studied the concentrations of phytoplankton in the oceans. Writing in Nature report "declines in eight out of ten ocean regions, and estimate a global rate of decline of ~1% of the global median per year". "We conclude that global phytoplankton concentration has declined over the past century" and "long-term declining trends are related to increasing sea surface temperatures." Since phytoplankton, minute plants, "account for approximately half the production of organic matter on Earth" this could be bad news.

Marine phytoplankton
According to a Reuters story, "The study estimates the decline in marine algae has been approximately 40 percent since 1950." Half of all photosynthetic carbon fixation, cut by 40%!? That's significant and scary.

The story quotes study co-author Boris Worm: "I think that if this study holds up, it will be one of the biggest biological changes in recent times simply because of its scale. The ocean is two-thirds of the earth’s surface area, and because of the depth dimension it is probably 80 to 90 percent of the biosphere. Even the deep sea depends on phytoplankton production that rains down. On land, by contrast, there is only a very thin layer of production."

Here is an excellent release in Science Daily summarizing the report.

Yield Reductions in China?

A review paper in Nature by Shilong Piao et al. assesses "the impacts of historical and future climate change on water resources and agriculture in China. They find that in spite of clear trends in climate (especially temperature), overall impacts are overshadowed by natural variability and uncertainties in crop responses and projected climate, especially precipitation. In a best-case scenario, crop production is constant, whereas the worst-case scenario suggests that production could fall by about 20% by 2050." (From Editor's Summary.)

A Reuters article quotes further from the paper, "Countrywide, a 4.5 percent reduction in wheat yields is attributed to rising temperatures over the period 1979-2000," and says "They forecast that rice yields would decrease by 4 to 14 percent, wheat by 2 to 20 percent and maize by zero to 23 percent by the middle of the 21st century."

(Grist carries an AFP story about this research.)

What Does It Mean?

These results from several unrelated fields of research suggest that we should be concerned that continued warming will negatively affect both wild plants (which act as a carbon dioxide sink) and agriculture (fundamental to social stability).

If forests, grasslands, phytoplankton in the sea and other ecosystems absorb less of the CO2 we release by unrestrained burning of fossil fuels, then atmospheric CO2 levels may rise faster than models currently predict.

If higher temperatures and drought reduce agricultural output more land will have to be brought under the plow. Such land-use changes usually release significant additional carbon dioxide.

We should significantly increase spending on agronomy and plant breeding, especially in Africa, India and East Asia, if we want to maintain the yields we have.