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Climate Change: What are the facts? What I am trying to do I am very concerned about climate change, and am frustrated that so little seems to be happening to prevent it. However, I recognize that it is a very technical subject and that scientific understanding is moving rapidly. Therefore there is a need to present the current consensus view of the scientific community in a form that is comprehensible to the intelligent lay reader. Consequently I have gathered together background information, current scientific knowledge, expert opinion on likely future consequences, and political responses. Dr Stephan Harrison, climate expert at the University of Oxford has read this document and he wrote: “I'm happy to say that I agree that the scientific aspects represent the general consensus of climate scientists.” What I would like you to do Please read what I have written below. To keep it as simple as possible, I have put some of the science and all the references at the end. You don’t need to read them, but please do if you doubt anything. Please decide whether you agree that there is a compelling case for immediate and drastic action to reduce climate change, and let me know what you think in terms of the science and what should be done. ‘Basic’ Facts Climate change is a complex subject, so it would take hundreds of pages to explain all the background. However, I hope that the following is sufficient! The sun’s rays heat the earth. The earth cools by giving off infrared rays. If there is more heating than cooling, then the earth warms up. However, the earth is very large, so it takes about 30 to 40 years to heat up. The atmosphere contains carbon dioxide, methane and nitrous oxide. These gases, together with water vapour, stop some of the infrared rays escaping from the earth: this is the natural greenhouse effect. By increasing some of these heat-trapping gases, and adding new ones, we heat up the earth. The Lessons from History The Great Dying, occurred approximately 252 million years ago. It was the Earth's most severe extinction, with the extinction of up to 96% of all marine species and about 70% of terrestrial vertebrate species. It is known that huge volcanoes in the Siberian traps released large quantities of carbon dioxide and sulphur. This lead to a major increase in temperature, probably triggered other events such as the release of vast quantities of methane from the sea bed, killing off most of the life on earth. To and from the Ice Age Very dramatic climate changes occurred at the end of the last ice age between 20,000 and 10,000 years ago. For instance, during the Younger Dryas cooling event the temperature in parts of the North Atlantic fell by 80C very quickly: perhaps within 10 years, and definitely within a 50 years period. Similarly, very dramatic changes happened at the end of this period when temperatures rose by about 6-80C. 1 Around half of the warming seems to have occurred in the space of a single span of 15 years. What is happening now? Temperature and CO2 levels Each year we add more than 30 billion tons of carbon dioxide (CO2) to the air, mainly by burning fossil fuels and cutting down and burning trees. We also emit other greenhouse gases. The UK emits about 156 million tons of carbon, and with the other gases, the equivalent total is 199 million tons of carbon. Global temperature has risen by 0.7oC in 100 years and is rising at about 0.2 oC every decade. Glaciers Throughout the world, glaciers are melting. At current rates, there will be no glaciers left in Africa in 15 years. This melting of mountain glaciers is one reason for rising sea levels and a clear sign that climate change is real and global in extent. Greenland ice sheet The edges of the Greenland ice sheet are clearly melting. Unless there is a catastrophic event, it should take hundreds of years for all this ice to melt. However, if it does melt, the sea level will rise by over 7 metres. Extreme Weather There is the possibility that there has been an increase in the frequency of ‘extreme weather events’ caused by climate change. For example, drought in Australia, hurricane Katrina, recent floods and the extreme heat wave in Europe in 2003 which killed thousands of people may have been caused by climate change. Marine acidity Something like half of the extra carbon dioxide caused by human activity is absorbed by the oceans. So far, this has reduced the impact of climate change, but is turning the oceans acidic. This seems to be one of the factors causing the death of coral reefs. Faster plant growth It is not all bad news. The increased levels of carbon dioxide in the air may mean that plants can grow a little bit quicker. Dangers Ahead By the end of the century, global temperature is expected to rise by between 0.60C if there are no overall greenhouse gas emissions (not going to happen!!) and 4.00C (perhaps as much as 6.40C ) with fossil fuel intensive economic growth. Forests As the climate changes, the habitats of plants (and animals) will change. Most places are getting hotter, some places will become drier, and others will become wetter. Of particular concern is the expert opinion that a rise of 2 or 30C might kill the Amazon rainforest and the broad-leaved forests of China. Most worrying, a 40C rise is predicted to cause the extinction of more than 40% of all species. Marine Life The increasing acidity of the oceans is making it increasingly difficult for marine life. Thus, there is a chance that in the near future, a large proportion of the world’s marine life will die. This includes plankton, seaweeds and fish. Methane Rotting plants and animals naturally give off methane. Much of this methane is trapped in permafrost and under the oceans. Permafrost covers about half of Canada and half of Russia and is up to 800 metres deep. As the earth warms, the permafrost will begin to melt, and the oceans will warm. This will release the trapped methane into the air and the melting of permafrost ice will increase sea levels. 2 Sea Level As the earth warms, snow and ice melts, sending water into the oceans. In addition, water expands as it warms. These two effects have already lead to the sea level rising; but probably only by about 0.5 m so far. However, the danger is that significant portions of the Greenland or Antarctica icesheets may melt leading to massive rises in sea level. Greenland has enough ice to produce a 7m rise in sea level, and Antarctica has enough ice for a 35m rise. Clearly even a small percentage of these quantities would lead to the drowning of many of the earth’s major cities and a large proportion of agricultural land. If this happened, then it would be inevitable that millions of people would die as a result. Antarctic A rise in sea level and a small temperature rise could be enough to break up the marine ice shelves in Antarctica. Removing this ‘barrier’ to the land-based ice may allow vast quantities of ice from the continental interior to slip towards the sea. Once this happens, friction can melt the ice at the bottom allowing it to slide even faster, causing an ‘ice armada’. This has happened in the past, so it is quite possible it will happen again. An ice armada could cause sea level to rise by several metres in a very short time. This is a very serious threat as it could easily drown much of UK including London, costal towns and the rich agricultural fens in East Anglia and Lincolnshire. The Run-away Greenhouse As the earth warms, its response will change, for example: Snow and ice reflect sunlight, so when they melt, more sunlight is absorbed by the earth, heating it faster. When forests die, they will give out large quantities of carbon dioxide. This leads to a further increase in temperature as carbon dioxide is a greenhouse gas. In addition, there will then be fewer plants absorbing carbon dioxide, so the problems will rapidly increase. Also, if marine life dies, then it will stop being able to absorb carbon dioxide; thus speeding up the greenhouse effect. Similarly, there is a lot of carbon in soil. If the plant cover disappears, then this carbon, too, will be released into the air as carbon dioxide. Hotter water is less good at absorbing carbon dioxide, so as the oceans warm they may start releasing carbon dioxide back into the air, rather than absorbing it. Methane is around 20 times stronger as a greenhouse gas than carbon dioxide, so methane released from permafrost, from under the oceans and from other land may rapidly increase the earth’s temperature. These five effects create a vicious circle: a warmer earth leads to fewer plants, less carbon dioxide in the oceans, and the release of methane. All these factors increase the greenhouse effect and so create a warmer earth that then leads onto even fewer plants, more release of methane…etc. This is one way in which a run-away greenhouse effect could start. Most scientists agree that once it starts, it will be impossible to stop. This will lead to massive rises in sea level, drowning much of the land, including major cities and farming land. In addition, the widespread destruction of the biosphere will mean that many crops will not grow, there will be very widespread famine and quite possibly the collapse of our civilisation. 3 When?? Some scientists believe it is already too late and that some of the vicious circles described above are already happening. Others believe there may be a few more decades until it is too late. Urgent, sustained and immediate action is the best decision for the following reasons: • The earth takes 30 to 40 years to respond to any changes in greenhouse gases. So even if we stop all fossil fuel based transport, stop all heating using coal, oil and gas, and stop producing electricity from fossil fuels, then the earth will still carry on heating for 30 to 50 years becoming about 0.6oC hotter. Clearly no-one intends to take such drastic action. • As more countries develop and become richer, there are more people adopting a Western, energy-rich life-style. Currently, this is particularly true of China and India. Consequently, projections are for massive and sustained increase in use of fossil fuels. Therefore, the earth’s leaders are ‘anticipating’ a 62 percent increase in emissions of carbon dioxide in the next 25 years. • As explained above, once the run-away greenhouse effect starts, the vicious circles increasing the earth’s temperature will make it impossible to stop. Political Action Clearly we have a system in which the people in rich countries are using far too much fossil fuel for industry, transport, heating and food. People in poorer countries are aspiring to our way of life, and are trying to dramatically increase their use of fossil fuels. However, this pursuit of material wealth will certainly lead to devastating climate change that will destroy all that we are trying to achieve. Therefore it is madness to continue on this path. It is not known whether we are too late to stop devastating climate change, or whether there are a few more years before we reach the point of no return. However, current global emissions are set to rise relentlessly, despite the clear message from climate change researchers that this is endangering the whole of human civilisation. The only sensible approach is to accept that the best available scientific evidence is that we must make dramatic changes to our generation and use of energy. The sooner we make these changes, the less disruptive it will be for society and the better our chance of a better world. I have great faith in the ability of industries to adapt given the right economic incentives. I also have great faith in ordinary people to ‘do their bit’, if there is a clear message that this is the best way for us to maintain a high quality of life. So the major problem is to convince the politicians that drastic action is needed now. Politicians are slowly acknowledging that threat, but have consistently adopted policies that would do too little, too late and promote economic growth that increases carbon emissions. The House of Commons Environmental Audit Committee has damned the government’s stance, despite the fact that 10 out of 16 of its members are Labour MPs. In their report also published in March 2005, they wrote that, “Governments must act as a matter of urgency and on an unprecedented scale: a Marshall plan for climate change is now required.” And they reported that, “Sir David King has suggested that the UK’s 60% carbon reduction target which the UK Government has set for 2050 may need to be 4 increased to 80%.” And they concluded that, “The challenge of climate change is so great that action is required on all fronts if we are to achieve the scale of emission reductions required … it is simply not credible to suggest that the scale of the reductions which are required can possibly be achieved without significant behavioural change. In focussing on science and technology, the Government is creating the appearance of activity around the problem of Climate Change whilst evading the harder national and international political decisions which must be made if there is to be any solution.” The Global Commons Institute has proposed the Contraction and Convergence (C&C) model to combat climate change. In this model, the carbon dioxide emissions of all countries are reduced (contraction) and converge to an equal amount on an annual per capital basis. This is generally seen as the only fair approach, and is becoming more accepted. However, despite many politicians saying that they support contraction and convergence, their policies show that they are not committed to its success. It is interesting that the Archbishop of Canterbury said: “C&C thinking appears utopian only if we refuse to contemplate the alternatives honestly.” Simple maths shows that an 80% reduction by 2050 requires a 2 to 3% cut in carbon dioxide emissions per year. Anything less is disaster and many people are saying this will be too little. In addition, global action is required to increase the ability of the biosphere to absorb carbon dioxide (such as growing more forests). My request to you Congratulations for reading this to the end! You will have gathered that I believe climate change threatens: the extinction of most species on earth; to kill most of the human population; and, to destroy our current civilisation. I would be delighted if you told me your honest opinion. If you don’t believe me, please point out the holes in my argument or where there are difficulties in understanding. Many people don’t believe that the threat of climate change is as serious as I’ve indicated: perhaps they’ve read something in the paper or seen it on TV. However, the scientific evidence and the consensus of climate change scientists are overwhelming. Please contact me or go to http://gristmill.grist.org/skeptics if you would like answers to arguments from sceptics. Very many thanks, Ian Davison [email protected] Updated 2nd October 2007. 5 Further information You don’t need to read this, but below is scientific information and references under the same headings as before. What I am trying to do Dr Stephan Harrison’s website is http://www.geog.ox.ac.uk/staff/sharrison.php . Basic Science Incoming short-wave radiation (mainly visible light, ultraviolet light and short-wave infrared rays) from the sun heats up the earth. The earth cools, largely by giving off longwave infrared radiation. When these two processes are exactly balanced, then the earth stays at the same temperature. Radiative forcing is a measure of the influence a factor has in altering the balance of incoming and outgoing energy in the Earth-atmosphere system, and is an index of the importance of the factor as a potential climate change mechanism. It is expressed in Watts per square metre orWm−2 (see page 5, IPCC 2001 reference given below). Therefore the heating effect is stronger when the radiative forcing is greater. The power of the sun’s rays is 1370 watts per metre squared (Wm-2) when it reaches the earth. You will see in the table below, that the radiative forcing from carbon dioxide is roughly 1.5 Wm-2. This is tiny compared with the power of the sun; but this small effect over many years is gradually warming the earth. The Great Dying More formally this is called the Permian- Triassic extinction event. The entire extinction probably only lasted 80,000 years and showed distinctive phases in the plant and animal fossils they contained. The extinction appeared to kill land and marine life selectively at different times. The increase in carbon-12 over time has led to the suggestion that the increased temperatures also released huge volumes of methane gas from the sea bed. (See http://en.wikipedia.org/wiki/Permian_extinction.) Also see Peter Ward, Impact from the deep. Scientific American, 295, (4) 42-49 which suggests that for mass extinction, the greenhouse gases cause climate change that leads to release of poisonous gases and destruction of the ozone layer. To and from the Ice Age The theory that methane was released is according to analyses of the Greenland ice core record (Taylor et al., 1997 and see Alley, et al. 1993. Abrupt increase in Greenland snow accumulation at the end of the Younger Dryas event. Nature, 362, 527-529. What is happening now? The next two figures are taken from pages 3 and 4 of Climate Change 2007: The Physical Science Basis Summary for Policymakers Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (http://ipcc-wg1.ucar.edu/ and http://www.ipcc.ch/WG1_SPM_17Apr07.pdf ) The table below shows the way that carbon dioxide, methane and nitrous oxide levels have increased since the start of the industrial revolution. At the moment, the amount of CO2 in the atmosphere is about 380 parts per million and rising by about 1.9 part per million each year. 6 FIGURE SPM-1. Atmospheric concentrations of carbon dioxide, methane and nitrous oxide over the last 10,000 years (large panels) and since 1750 (inset panels). Measurements are shown from ice cores (symbols with different colours for different studies) and atmospheric samples (red lines). The corresponding radiative forcings are shown on the right hand axes of the large panels. 7 FIGURE SPM-2. Global-average radiative forcing (RF) estimates and ranges in 2005 for anthropogenic carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and other important agents and mechanisms, together with the typical geographical extent (spatial scale) of the forcing and the assessed level of scientific understanding (LOSU). The net anthropogenic radiative forcing and its range are also shown. These require summing asymmetric uncertainty estimates from the component terms, and cannot be obtained by simple addition. Additional forcing factors not included here are considered to have a very low LOSU. Volcanic aerosols contribute an additional natural forcing but are not included in this figure due to their episodic nature. Range for linear contrails does not include other possible effects of aviation on cloudiness. Temperature and CO2 levels “The global atmospheric concentration of carbon dioxide has increased from a preindustrial value of about 280 ppm to 379 ppm3 in 2005. The atmospheric concentration of carbon dioxide in 2005 exceeds by far the natural range over the last 650,000 years (180 to 300 ppm) as determined from ice cores. The annual carbon dioxide concentration growth-rate was larger during the last 10 years (1995 – 2005 average: 1.9 ppm per year), than it has been since the beginning of continuous direct atmospheric measurements” page 2 of IPCC physical basis report (reference given above). Predicted temperature rises are given in the same report. 8 http://en.wikipedia.org/wiki/List_of_countries_by_carbon_dioxide_emissions for emissions per country DEFRA publishes figures for the UK emissions (http://www.defra.gov.uk/environment/statistics/globatmos/index.htm ). In 1997, the UK emitted 548 million tons of carbon dioxide (MtCO2) and the equivalent of 706 MtCO2 including other green house gases such as methane and nitrous oxide. By 2005, these figures were 554 for carbon dioxide (i.e. gone up) and 656 total (i.e. gone down). So, overall emissions are falling slowly especially due to less methane from landfill sites, but there’s been no effective action to cut CO2 emissions. Glaciers Rignot et al. (2003 Science) provide evidence that the sea level is rising, partly due to the melting of temperate glaciers. Extreme Weather The extreme heat wave in Europe in 2003 which killed thousands of people is likely to be a product of climate change (Stott et al Nature 2004). In recent decades, there has certainly been a huge increase in the number and severity of El Nino years. The science behind this is complex, but seems to be linked to climate change. Faster plant growth and dangers ahead Although there is evidence of faster plant growth, recent research shows that plant growth in a warmer world (even with enhanced carbon dioxide levels) may be restricted because of changes in nitrogen levels and water supply. At the moment, the biggest impact (in climate terms) is that forests in the northern hemisphere are growing slightly faster, thus absorbing a little of the excess carbon dioxide. But these are also drying out, so the good news may not last for long. There are many detailed predictions in Climate Change 2007: Impacts, Adaptation and Vulnerability Working Group II Contribution to the Intergovernmental Panel on Climate Change Fourth Assessment Report (http://www.ipcc.ch/SPM13apr07.pdf ) see figure below for a summary. 9 Table SPM-1. Illustrative examples of global impacts projected for climate changes (and sea-level and atmospheric carbon dioxide where relevant) associated with different amounts of increase in global average surface temperature in the 21st century [T20.7]. The black lines link impacts, dotted arrows indicate impacts continuing with increasing temperature. Entries are placed so that the left hand side of text indicates approximate onset of a given impact. Quantitative entries for water scarcity and flooding represent the additional impacts of climate change relative to the conditions projected across the range of Special Report on Scenarios (SRES) scenarios A1FI, A2, B1 and B2 (see Endbox 3). Adaptation to climate change is not included in these estimations. All entries are from published studies recorded in the chapters of the Assessment. Sources are given in the right hand column of the Table. Confidence levels for all statements are high. Sea Level As the earth warms, snow and ice melts, sending water into the oceans. In addition, water expands as it warms. These two effects have already lead to the sea level rising; but probably only by about 0.5 m so far. However, the danger is that significant portions of the Greenland or Antarctica icesheets may melt leading to massive rises in sea level. Greenland has enough ice to produce a 7m rise in sea level, and Antarctica has enough ice for a 35m rise. Clearly even a small percentage of these quantities would lead to the 10 drowning of many of the earth’s major cities and a large proportion of agricultural land. If this happened, then it would be inevitable that millions of people would die as a result. Antarctic The consensus view in 2001 was that the Antarctic ice-sheets were probably stable, and would only melt very slowly (i.e. over thousands of years). However, this view has changed in the last few years. Scientists now speak of possible destabilisation. The contribution that rapid thinning of the Antarctic ice sheet is making to global sea-level rise is a cause for concern according to Director of British Antarctic Survey (BAS), Professor Chris Rapley. He said, "Satellite measurements tell us that a significant part of the West Antarctic ice sheet in this area is thinning fast enough to make a significant contribution to sea level rise… There is real cause for concern." Feb 2005 http://www.antarctica.ac.uk/press/press_releases/press_release.php?id=56 The Run-away Greenhouse Methane is around 20 times stronger as a greenhouse gas than carbon dioxide, so methane released from permafrost, from under the oceans and from other land may rapidly increase the earth’s temperature. See Bruce Buffett and David Archer, 2004 ‘Global inventory of methane clathrate: sensitivity to changes in the deep ocean’ Earth and Planetary Science Letters 227 185– 199. When?? CO2 in the atmosphere is rising fast. “According to Dr Tans, one significant finding is that the annual rate at which the CO2 is rising has itself increased. The growth rate over the past decade was about twice as fast as that found in the 1960s” (see http://news.bbc.co.uk/1/hi/sci/tech/4395817.stm ). It is possible that we are already starting the run-away greenhouse effect; perhaps because the oceans are no longer absorbing as much CO2. However, it is not clear when the other 4 vicious circles mentioned above will start to have an impact. The expert judgement of Hansen et al is that “a CO2 level exceeding 450 ppm is almost surely dangerous, and the ceiling may be even lower… Have we already passed a “tipping point” such that it is now impossible to avoid “dangerous” climate change…? In our estimation, we must be close to such a point, but we may not have passed it yet.” Hansen et al (2007) ‘Dangerous human-made interference with climate: a GISS modelE study’ Atmospheric Chemistry and Physics 7, 2287–2312 http://www.atmos-chemphys.net/7/2287/2007/acp-7-2287-2007.html The 2004 World Energy Outlook of the International Energy Agency calculates that in the next 25 years, global emissions of CO2 are likely to increase by 62 per cent. Political Action The House of Commons Environmental Audit Committee report can be found at: http://www.gci.org.uk/briefings/EAC_Final_C&C.pdf The global commons institute website is at: http://www.gci.org.uk/ See http://www.gci.org.uk/speeches/Williams.pdf for the 2004 the Archbishop of Canterbury quote. 11