320^th Meeting – Tuesday, February 9^th 2010

New Strategies to Stop Global Warming

A talk and presentation by Dr. Michael Tuckson

 
Present: Joup Schillemans, James Emmanuel Bogle, Klaus Berkmüller, Adrian Pieper, Sjon Hauser, Richard Nelson-Jones, David James & Mangkhoot, David Steane, Patricia Cheesman, Susan Morgan, Kunakorn Boonsai, Dianne and Mark Barber-Riley, Oliver Hargreave, Reinhard Hohler, John Cadet, Suttida Sudadokfah, Duanpen Chaladlam, Natthirah Kramer, Daniel Bellamy, Anna Willen, Chris White, Joel Akins, Bodil Blokker. An audience of 25 plus probably six more who didn’t sign in.

Michael’s summary of his talk and presentation:

Global warming and climate change will affect everyone’s future, possibly in a devastating way. It is a highly complex topic, and based on difficult science, making it hard to understand. Moreover, the solutions require significant sacrifices in the lives of people in the modern sectors. This has given rise to widespread resistance, resulting in mental denial of the truth of the science. Perhaps the greatest immediate threats to our wellbeing and even existence are the widespread ignorance of thermal inertia, feedbacks and tipping points in surface earth systems, together with the power of finance. It is hopeful that deniers are not simply selfish, but have blocked learning about the latest climate science, and are thus open to dialogue or subtle education. Change will be made much easier if the pain is shared.

Rapid Meeting Survey

To give me some idea of the audience’s feeling, they were asked to choose the closest option to their thought and action about global warming from a range of 15 alternatives. One person denied the Earth is warming. Four said they were sceptical that we can stop the warming as society is not up to it, and one didn’t know enough to express an opinion. Five said they were pessimistic that we can stop it but were willing to try and help, one said she was studying the issue, but not yet active. One knew a lot but was inactive as had no time, one was occasionally activist, but not sure of the best strategy in Chiang Mai, and four were activist with an ongoing programme. Total of 18. I think several didn’t volunteer an answer.

Climate Science

Global warming is not just global warming but a rise of climate extremes and sea invasion. The rainy areas will experience bigger floods and the drier areas more severe droughts. Some areas will experience more extreme heat waves and associated forest fires, while some will become more stormy. James Hansen in his book Storms of My Grandchildren (2008) points out that the melting ice sheets will result in more icebergs that will in turn raise the ocean temperature gradient between the tropics and the polar regions, causing stronger storms.

We are now entering a condition best described as the climate emergency for four reasons. First, the climate is changing more rapidly. Second, earth inertia and feedback are better understood. Third, we are mentally and physically set in a complex system, hideously difficult to change, amounting to social inertia. Fourth, resistance and denial have been promoted by extremists, and are spreading through the traditional and online media to ordinary people. Some hope is provided by Paul Ray’s (2003) analysis of the growing cultural movement, notably in the USA, that rejects left-right debates.

I have described denial (skepticism is mainly a front term) as a virus as it is evolving with the progress in science and the worsening conditions, changing from denying the warming, to denying the human dominance, to denying its importance. It also uses increasingly aggressive techniques, from claiming scientific uncertainty to claiming scientific fraud. It has recently begun jumping on individual errors to claim a global collective error. Climate science is a difficult subject, but if your knowledge is limited it is easy to misunderstand and be misled by the ill informed and the devious. In discussions about global warming, climate science must come first. We must all be able to counter the cherry picking, apparent misunderstandings, distortions and downright lies of the deniers, both from the ‘leaders’ or seniors and the devious and innocent followers. The devious focus on the science as they know most people do not understand. So all concerned must rise to the challenge, and the challenge must be seen to be global, not simply local. The challenge now will have to be smarter just as medicine must rise to face evolving viruses and bacteria. This is the first strategy. It is worth noting that science is never a total consensus, but has levels of consensus that change over time and vary with exact topic.

Following are six points that can be used to counter deniers. One good way is to show then-and-now photos of glaciers and Arctic ice. The NASA GISS temperature data trend shows clearly that the Earth is warming even with yearly or two yearly oscillations driven by the ocean (GISS website). The last decade has been the warmest for thousands of years. From 1945 to 1975 the northern hemisphere warming was slowed by sulphate aerosol pollution, but in the less developed and ocean dominated south, aerosol pollution had less effect (IPCC 1977). Deniers cannot explain this. Climate models that include the natural and human factors explain the average warming best (Stott et al., 2000). Solar radiation changes by 1 percent over the 11 year cycle, but over the last two decades has on average been cooling to steady while the earth has warmed considerably. That other proposed extra-terrestrial influence, cosmic rays, that also oscillate, have been shown to be unrelated to the formation of clouds that might cause warming (JE Kristjansson et al., 2008).

Critical Concepts

Three useful concepts measure the influence of the GHGs and dusts and aerosols. The instantaneous changed influence of each greenhouse gas and dust is called Radiative Forcing. This is the changed influence since the beginning of the industrial revolution due to increased concentration. Some dispute between scientists is evident over the quantities for each substance. Carbon dioxide equivalent is a summation of forcing of six GHGs recognized by Kyoto converted to a concentration measure. The quantity is somewhat higher than the figure used for carbon dioxide alone, but whether it is high enough is not clear. It does not include aerosols and dusts. It is also rarely clear which researchers are using it and which are not!

Global Warming Potential (GWP) is the influence over time into the future compared with carbon dioxide. Carbon dioxide concentration falls to half in about 24 years and half that again in about 140 years (Hansen et al 2007). In contrast, methane has a half life of seven years, meaning an emission at one time declines in concentration by one half in seven years. Its GWP is thus only high for the first few years after emission. Some researchers are calling for more attention to be put on methane and other short-lived GHGs and dusts partly because of their high short-term GWP{Mohr (2005) Goodland and Anhang (2009) and Molina et al (2009). GHGs spread world-wide.

In contrast the dusts and aerosols are regional. Black carbon soot is prevalent in poor rural regions such as China and central Africa. It is a serious problem over the Ganges as it drifts northwards raising snow and ice melting rates in the Himalayas and Tibet, the source of seven huge rivers. As the glaciers recede, the river flow in summer will fall correspondingly. The black carbon comes from homes, farms and diesel engines. Soot from Europe was having a detrimental affect on Tibet, northern Pakistan/India and Nepal up until the 1970s. But since the rise of early forms of pollution control, the main remaining source for Tibet is the Ganges basin (Xu et al, 2009; Bachmann, 2009:).

It is useful to have at least a rudimentary knowledge of the carbon cycle in the surface earth system, as deniers use the poor popular understanding to confuse. Carbon is found mainly in four Earth stores, the atmosphere, forests, soil and ocean. Much carbon moves back and forth between the atmosphere and the other three, maintaining a rough balance. The human contribution by fossil fuel burning and forest clearing is annually only a small proportion of these flows, but a critical one, as over decades it is building the concentration in the atmosphere to dangerous levels and destroying the former balance. The other three stores cannot cope with the atmospheric increase although they take in some.

Because of thermal inertia in surface Earth systems, carbon dioxide already in the atmosphere, now at 387 ppm, guarantees another 0.5 to 0.6 degrees of warming. We are now virtually at 1.3 -1.4 degrees above, not 0.8 (Hansen et al., 2005). This means that if we cannot capture the excess carbon dioxide already in the air, we are guaranteed a sea level rise of at least 4 metres and probably much more, based on the experience of Earth history. Glikson (2008) notes that about 120,000 years ago sea levels rose about 6-8 metres above present levels due to a rise of about one degree above present levels. Thus, we must not only stop emissions, but plant hundreds of millions of trees and store the carbon grown in building and biochar. This requires a massive global education programme.

Surface earth system feedbacks are already operating, but if they become dominant, Earth will warm beyond human control to at least 6 degrees, causing climate change too severe for most humans and other organisms to survive. Feedbacks of three types (at least) are relevant. The first is fast amplifying (positive, warming) feedback. Since early industrial times, increasing evaporation from a warming ocean has been causing increased water vapour in the atmosphere causing further warming. It is now thought that water vapour might be causing 30 percent of warming overall. The second is slow amplifying feedback’ such as methane released from permafrost, but which is already starting. An example of negative or cooling feedback, is desert dust reflecting sunlight (Hansen et al., 2008). Climate scientists are sure that amplifying warming feedbacks will dominate cooling ones.

Tipping points and irreversibility are two other critical concepts. A tipping point occurs when a change is qualitatively different and usually, but not always, faster than the cause. The change is often described as non-linear, meaning really not in a straight line. They are important in large biophysical regions, systems or elements such as a large forest region or ice sheet. Tipping tends to, but not necessarily, lead to irreversibility (Lenton, 2007, Copenhagen Diagnosis, 2009). The significance of tipping points is that they tend to make the environmental degradation process both faster and harder to reverse.

Palaeo-climates

Studying Earth’s climate history is making an increasing contribution to climate science. Including feedback in climate models is difficult, but palaeo-climatic change includes feedbacks such as the rise of water vapour or carbon dioxide in the observed changes, and can elucidate the long-term carbon cycle. The Earth’s surface has generally been cooling even though the sun is getting brighter very slowly. This is due to the increased storage of carbon dioxide in limestone, and sedimentary rocks high in plant carbon, buried deep in the earth.

Major cold-warm Earth cycles covering 100 or 200 million years are due to plate tectonics. Sustained volcanic and related events cause emission of carbon dioxide that result in long warm periods, while the burial of carbon rich rocks cools the Earth. No other viable explanation that does not involve carbon dioxide has been put forward. Although cosmic rays appear to be partly correlated with these climate cycles no viable causal explanation has been advanced.

If mountains or other uplands are formed, the weathering of earth material rich in plant carbon result in the natural emission of carbon dioxide to the air. Forest and phytoplankton growth under the right conditions leads to the formation of rocks that may become fossil fuels. Other rocks are weathered mainly by carbonic acid that results from the combination of carbon dioxide and water in the atmosphere and soil. Together with erosion, this results in the transport of bicarbonate ions to the sea. In relatively alkaline, shallow, warm water with, largely free of mud and sand, limestone is deposited. The surface cools when these high carbon sediments are buried in sufficient volumes, without further carbon emissions from the deep Earth. This leads eventually to the expansion of glacial regions and the formation of tillite sediments. This is the long term Earth or geological carbon cycle.

The formation and melting of ice sheets in Antarctica about 30 million years ago was caused by a fall and then rise of 2 degrees in temperature. The atmospheric concentration of carbon dioxide was about 500 ppm when it began to melt.

Smaller climatic cycles about 100,000 years from peak to peak are clearly observable in the Pleistocene ice and sediments deposited over the last 1.8 million years. These short cycles are initiated by changes in Sun-Earth geometry that change the distribution of temperature near the poles. Subsequently amplifying feedbacks due to water vapour, ice melting and then carbon dioxide, and may be methane, cause major changes, and make them global. Warming due to feedback follows several hundred to a few thousand years after the geometry change. Deniers are fond of noting that the temperature rise takes place before the carbon dioxide rise but fail to mention the influence of Sun-Earth geometry, ice melting or evaporation. Whereas carbon dioxide was only the fourth influence on warming in the Pleistocene cycles, it has been the main trigger in the last 200 years.

Interglacial warm periods in the Pliocene (5.5 – 2 million years ago) and Pleistocene were warmer by 2-3 degrees above the present time. Carbon dioxide levels were at 500-550 ppm and sea level was 25-35 metres higher than today (Glikson, 2008).  One billion people globally now live/work at less than 25 metres above sea level. 500 ppm is just a little over the value that big governments are “aiming” at. What is the danger (commonly called “risk”) that we would exceed that figure of 450 ppm? Moreover, we can be fairly sure that 450 ppm already involves a sea level rise of the order of 20 metres.

Conditions and the Future

James Hansen and his teams put the risk or danger of losing control of our climate higher than the IPCC, including seemingly those scientists who wrote the Copenhagen Diagnosis. What risk is acceptable of say crossing the 1.5 degree threshold that the vulnerable nations have sought? What is a reasonable danger that your descendants will face misery or even die from climate change? My understanding of the danger has increased since reading James Hansen’s team’s recent scientific papers and accounts of melting and break offs in Antarctica and Greenland.

Although the predictions are always uncertain, Earth’s thermal inertia means that for humans to survive in the long term we must absorb much of the carbon dioxide already in the atmosphere. Not only must humans stop the global temperature rise before 1.5 degrees Celsius above pre-industrial levels and before we reach 430 ppm carbon dioxide, we must also bring the CO2 concentration down again to below 350 ppm (Hansen, 2008), and to 300 ppm (Spratt and Sutton, 2007). We must also reduce emissions of the other warming gases and dusts, keeping in mind that sulphate aerosols that reduce warming are short lived, so that reducing carbon dioxide emissions will result in a sudden drop in their influence, even though the emitted carbon dioxide is long lived. Could we soon face a global tipping point? We are now at a virtual 1.3 degrees, not 0.8 degrees above pre-industrial temperature. If we consider all the human induced environmental degradation as well as all the feedbacks from ocean heating, ice melting, forest dieback and fire, forest type migration, permafrost melting and the giant, methane ice emission, feedback and irreversibility could take over. Can we stop it?

We must encourage and show effective leadership, based on knowledge of the latest science and strategies, at as many levels as possible. The Northern Europeans, Brazil and the small island nations are leading, but few others are following. In our hour of need, the schooling systems and mass media, even the best ones we can muster in so-called developed nations, are failing us. Curricula are over specialized in at least two levels of schooling, and the mass media pushes political theatre to sustain audiences. 

When we consider responsibility, human lifetime emissions should be used as a criterion to compare nations. If we compare historical emissions, Britain leads. If we look at national emissions now, China leads, and if the comparison is per capita, Canada is out in front. But if we consider emissions over individual human lifetimes, what to me is the fairest basis for comparison, which nation will hit the top? What matters more is that we all as individuals have various lifetime responsibilities.

The Origin of Denial

Geography and history must be considered as well as pollution morality. The ex-white British nations, rich in fossil fuels and other resources per capita, with sparse populations, cavalier and materialistic, the growth of giant corporations, as opposed to more subtly cultured, are high polluters and leaders of denial. The USA started with old Protestant Christianity, slavery, invasion of the native populations’ land, and cowboy culture in the West of a huge space (Jacoby 2008). It seems probable that deniers are led initially to their position by a life among plentiful resources, technological wealth, defensive ideologies, specialized schooling, sometimes religion and other cultural factors.

The USA won’t take to renewable energy like Denmark. That’s not because the Danes are brilliant environmentalists, but because of the different circumstances. Denial comes from a particular background, contemporary lifestyle, and for individuals, personality. This leads to refusal to learn outside the specialization. A major uncertainty in denial is the degree to which the deniers are simply selfish, the common assumption, and the degree to which they are ignorant of the latest science. I postulate that from corporate ease comes a sequence of mental actions, starting from a reluctance to study even simple climate science, followed by an interest in the claims of the early ideological deniers, blocking out of science-based ideas, then seeking out of denier theory, and for some eventually speaking out, or donation to think tanks. Most only express their denial privately or in polls. The particular geography and history and lifestyle leads to a refusal to learn new ideas that threaten the lifestyle. Even though James Hansen (2009) claims they all understand it, it seems probable that the influential and powerful deniers are at least partly ignorant of the latest science. It is not easy to understand this topic even if you dearly want to. This means that subtle education is probably still relevant.

Mitigation Strategies

The first strategy, as indicated above, is to learn enough of climate science to counter deniers in letters to papers, in online comment columns, videos and other fora. Those outside the USA should help it to change, not by lecturing, but through dialogue, albeit rapidly. We need an armada of letters and emails.

Because we find ourselves in an emergency, it is necessary to promote the idea of, and organize incentives for, behavioural change before appropriate technology is well developed. If we depend on changing technology to reduce emissions, the evidence suggests climate change may become severe and uncontrollable before it is widespread. We need to follow the precautionary principle when uncertainty is apparent. Behaviour change includes actions that rely on existing equipment, buildings and vehicles. Examples are turning off lights, sharing cars and eating less meat. 18 percent of US college students are already vegetarian, so we are on the way. Practices such as contraception, reducing farm burning and bicycling may involve small changes in technology. Although all behaviour changers will ‘save money’ those in the relevant production areas will lose out. It is therefore necessary that job-time sharing and retraining etc is part of behaviour change in order to limit mass unemployment and unrest. This generosity will help reduce denial in declining industries. But probably the key initial behaviour change required is a willingness to study, learn and teach locally and internationally to promote a vastly increased understanding of climate science in key populations around the world. Don’t feel shy about ‘teaching up’ and across rising seas. The seniors in the big nations have a lot to learn. Government leadership is of course a marked advantage.

The behaviour change must be mainly in the modern sectors of all nations, not neglecting the poor rural areas where the peasantry should be taught to drain any irrigated rice fields from time to time where water is adequate, helped to reduce black carbon soot emissions.

The effort must be collective, not individual, as one person using less fossil fuels allows the next one to use more. Thus all countries must participate in an international agreement. We must all put in effort towards that. Because individual effort is not enough, if your funds are limited, rather than buying still ‘expensive’ renewable energy, it is better to spend your spare funds studying, in dialogue with or teaching both the seniors and the mass of deniers. It also important to promote citizen agreements at local levels and through the World Wide Web.

Foreign aid must be offered that is sufficient for the poor to get access to basic low carbon energy, and more efficient stoves, to help them manage forests and plant trees, to understand rice field drainage, and for the women to get access to contraceptives.

Should we put nearly all our effort into adaptation or mitigation? The former will, in all likelihood, only have temporary value if we don’t go all out on the latter.

Different policies are required for different greenhouse gases such as carbon dioxide, methane and nitrous oxide, as well as the dusts. Nearly all the discussion in journals and the media now is for carbon dioxide. This is an error. Particularly methane and black carbon soot should be addressed decisively. A temporary substitute for cooling aerosols will be required.

It is worthwhile to look out for measures that have other advantages. Many useful practices cost less. Minimum tillages minimises soil erosion, biochar increases productivity is some circumstances. A balance is needed between ploughing and burning to manage stubble that minimizes emissions. Vegetarianism and veganism are healthier eating styles. Emission standards and increased energy efficiency reduce city pollution and total production costs. Surface coal mining destroys landscapes. Oil transport can pollute seas. Small cities that reduce commuting emissions are more pleasant places to live. From now they must be built of wood to help store the carbon. Ted Trainer has, over the years, documented many ways and advantages of simple, sustainable lifestyles.

Three main forms of government policy amounting to regulation and incentives for carbon dioxide are being discussed, namely, cap and trade, auctioned or not, carbon tax or fee, and rationing, each of which have strengths & weaknesses. Whichever is chosen, it must be based on understanding, sincerity, and be sufficient to have a major impact.

The advantages of cap and trade, if auctioned, are revenue for government, some prior knowledge of emission reduction, increased global efficiency, and a provision to assist poorer nations. The advantages of a carbon tax/fee are revenue for government, greater knowledge of revenue raised, flexibility, transparency, less lobbying, no offset uncertainty, and avoiding weakening poor nations’ drive to help themselves. Hansen (2009) has proposed that the revenue must be returned to the people on a per-capita basis. Rationing via permits has high equity, good knowledge of emission reductions, flexibility and transparency. All three provide an incentive to emit less. Because cap and trade has the major disadvantage that it is almost impossible to reverse, apart from lobbying and tree offsets, it would be better to at least start with a tax quickly, modified with learning over time, until the methods are more widely understood. The case for auctioned cap and trade can be put then as an alternative to an operating and better understood tax system.

For carbon dioxide, other measures that will be necessary, including learning support, are a halt to new fossil fuel projects, research and development grants to universities and similar research organizations, highway regulations, manufacturing, building and renovation codes for energy efficiency. As well we will need regulation and subtle development support for forest conservation, support for a massive tree planting and maintenance programme, incentives for minimum tillage and reduce burning of crop stubble and forest regrowth, where possible. Research is needed to compare minimum tillage and organic farming involving ploughing. As temperatures rise, forests and tree plantations are facing pest attacks, drought and fire. It will be worthwhile to cut major firebreaks and store the carbon if fire is probable. Offering subsidies for particular low carbon technologies, including of course nuclear, is a mistake. The market should be left to choose, once the overall incentive to change is in place. Nuclear has other issues, but note Hansen’s (2009) support for experimental fast breeder reactors.

Black carbon soot reduction requires better stoves for the poor and diesel filters. Methane reduction requires promotion of veganism, a tax on livestock, standards of emission from mines, pipelines and waste dumps. Nitrous oxide reduction requires a tax on nitrogenous fertilizer. The countryside cannot be omitted if we are to pull through.

All this requires a massive programme of multi-lingual, multi-national education. Not counting deniers, it is extraordinary to listen to those who are nonchalant about the timing of solutions as though we have decades to solve the problem, and that it will cost say just one percent of GDP. They are living in a dream world. 300,000 people are dying annually from climate change, a figure destined to rise alarmingly. When you close all the coal mines and stop oil exploration, shut down ranches and dairies, and plant hundreds of millions of trees, the costs will be more than one percent of GDP. But the pain must be spread, if we are not to die from violence before hunger.  

Persuading the Government

How can citizens persuade the government directly or indirectly? Should we call it education, persuasion or pressure? 17 strategies existing strategies such as writing, emailing directly, letters to newspapers, videos, face-to-face dialogue are in use. Videos could be made much more effective. Two strategies I haven’t seen tried before are what I am calling the hierarchical strategy and the people’s web strategy as described in my website. The hierarchical strategy involves a combination of group letter writing, face-to-face dialogue and learning support, focusing on one major local organization or branch, moving up the hierarchy. The aim is to inform and raise the understanding of the people at the top of hierarchies, eventually seeking to influence the president or prime minister of a nation. Through a people’s global web-based emission reduction strategy it may be possible, with coordinated leadership and people’s international agreements through the World Wide Web, that we can collectively significantly reduce net emissions. If we can all see that citizens of other major nations are making an effort it might catch on. City pairing could be effective.

Should we best be trying to educate the powerful or the mass? As denial spreads it becomes increasingly necessary to work with all the people, but with some focus on prominent deniers in major polluting nations. Contacting young adult children of senior deniers may be a useful strategy.

How Can Government Persuade the People?

How can a government that is already progressive on climate change persuade the people to support it where denial has spread widely? Within a few months we need much better videos that are well focused on the denier cases but using personal stories. These can be put in short and long spots on television and distributed to other media, government offices, schools, universities and corporations etc. Cartoons could usefully be employed. Governments could invite all politicians, department heads and CEOs to seminars/ dialogues led by the most fluent climate scientists backed up by the most knowledgeable.

Relatively long term approaches, and here I mean a few years only, challenging the capacity of people and governments, are to set up or expand existing government media organizations, improve schooling curricula at all levels and reduce lobbying from corporations on governments. Washington harbours many more corporate lobbyists than politicians. This must be outlawed or otherwise opposed. Emergency additional school/college/university curricula can be introduced if the relevant powerful fear the future.

See www.stopglobalwarming-newstrategies.net for further ideas and information.

References

Bachman, John, 2009. Black Carbon: A Science/Policy Primer. Pew Centre on Global Climate Change

Copenhagen Diagnosis, 2009. UNSW Climate Change Research Centre   www.copenhagendiagnosis.org

GISS website: www.giss.nasa.gov/research/news/

Glikson, Andrew, 2008. Implications of abrupt atmospheric changes in the recent history of Earth for 21st  Century climate projections. The Australian Geologist, Dec 2008.

Goodland, Robert and Anhang, Jeff, 2009.  Livestock and Climate Change.www.worldwatch.org 

Hansen, James, 2009. Storms of My Grandchildren.

Hansen et al, 2005. Earth's energy Imbalance: Confirmation and implications. Science, 308.

Hansen et al, 2007. Climate change and trace gases. Philosophical Transactions of the Royal Society

Hansen et al., 2008. Target Atmospheric CO₂: Where Should Humanity Aim? Open Atmos Sc. J.

(Web address for many of James Hansen's and team papers: http://pubs.giss.nasa.gov/authors/jhansen.html)

IPCC Report 4, 2007. Summary for Policy Makers.

Jacoby, Susan. 2008. The Age of American Unreason.

Kristjansson JE, 2008. Cosmic rays, cloud condensation nuclei and clouds – a reassessment using MOSIS data Atmos. Che. Phy 8

Lenton, Tim et al, 2007.  Tipping elements in the Earth’s climate system.   PNAS  

Mohr, Noam, 2005. A New Global Warming Strategy. www.EarthSave.org

Molina, Mario et al. December 2009. Reducing abrupt climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions. Proceedings of the National Academy of Sciences,  Vol 106, No. 49

Ray, Paul, 2003. The new political compass. paul@integralpartnerships.com

Spratt and Sutton, 2007. Target Practice and www.carbonequity.info

Stott, Peter and team's paper 'External Control of 20th Century Temperature by Natural and Anthropogenic Forcings' in Science (2000) www.sciencemag.org/

Xu et al., 2009. Black Soot and the survival of Tibetan Glaciers. PNAS