CLIMATE ACTION NETWORK'S CLIMATE CHANGE PRIMER
Scientific Consensus
The overwhelming majority of scientists are in agreement about the following fundamental assertions: 1) the world has been warming and will continue to warm for the foreseeable future, 2) the warming is largely due to human activity (burning fossil fuel - oil, coal and gas - and destroying forests), and 3) the consequences of rising temperature, in all projected futures, are grave enough to warrant global action.
How do we know this?
In 1988 the United Nations established the Intergovernmental Panel on Climate Change (IPCC) . This is a body of over 2000 scientists and experts from around the world who gather periodically to review the existing peer-reviewed literature of the relevant science. Scientists who might be skeptical of the IPCC's work are also invited and are even among the lead authors of working groups. The summary documents are reviewed word for word, with industry and skeptics in the room. The IPCC's methods are designed to be rigorously fair to dissent, and thorough. The IPCC only began to assert the fundamentals in 1995 and since then has increased the conviction of the wording in its summary statements.
To add to this unprecedented overall agreement of the world's scientists, a statement endorsing the legitimacy of the process and the conclusions of the IPCC (The Science of Climate Change) was signed by 16 national scientific societies in 2001.
In June 2005 a second joint statement (Global Response to Climate Change) was issued by the science academies of the G8 nations and of China, India and Brazil. It stated that "the scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action throughout the world"
From the joint science academies' statement: Global Response to Climate Change, June 2005:
"The existence of greenhouse gases in the atmosphere is vital to life on Earth - in their absence average temperatures would be about 30 centigrade degrees lower than they are today. But human activities are now causing atmospheric concentrations of greenhouse gases - including carbon dioxide, methane, tropospheric ozone, and nitrous oxide - to rise well above pre-industrial levels. Carbon dioxide levels have increased from 280 ppm in 1750 to over 375 ppm today - higher than any previous levels that can be reliably measured (i.e. in the last 420,000 years). Increasing greenhouse gases are causing temperatures to rise; the Earth's surface warmed by approximately 0.6 centigrade degrees over the twentieth century. The Intergovernmental Panel on Climate Change (IPCC) projected that the average global surface temperatures will continue to increase to between 1.4 centigrade degrees and 5.8 centigrade degrees above 1990 levels, by 2100."
In 2007, the IPCC released three "summary reports" (as a preamble to a comprehensive report) which examined the current science on climate change and the likely human and financial impacts in the years to come. Overall, the 2007 review rates the probability that human activities are the main cause of climate change at 90 percent, a dramatic increase from the same panel's finding of a 66 percent probability in 2001.
The 2007 IPCC review also examines the impacts of climate change on human populations and points out that the populations most affected (yet least responsible for increasing levels of greenhouse gas emissions) will be the world's poor.
In reviewing the financial costs of limiting long-term climate change, the 2007 IPCC review found that the expense of stabilizing greenhouse gases, to limit global warming to between 2°C and 4°C, is "negligible". Cost estimates are between 0.2% and 3.0% of global GDP by 2030. (The cost of not taking action, as noted in the UK Stern Review and elsewhere, is far higher.)
The Case of the Bogus Petition (and the dodgy "Swindle")
Over the past several years a petition against the IPCC's views and the need for the Kyoto Protocol has circulated, claiming to be signed by 19,000 American scientists.
The petition is a hoax, intended to spin the idea that there is no scientific basis for claims about global warming.
According to the Union of Concerned Scientists of the USA:
"The Marshall Institute co-sponsored with the OISM (Oregon Institute of Science and Medicine) a deceptive campaign -- known as the Petition Project -- to undermine and discredit the scientific authority of the IPCC and to oppose the Kyoto Protocol. Early in the spring of 1998, thousands of scientists around the country received a mass mailing urging them to sign a petition calling on the government to reject the Kyoto Protocol. The petition was accompanied by other pieces including an article formatted to mimic the journal of the National Academy of Sciences. Subsequent research revealed that the article had not been peer-reviewed, nor published, nor even accepted for publication in that journal and the Academy released a strong statement disclaiming any connection to this effort and reaffirming the reality of climate change. The Petition resurfaced in 2001."
In fact, American experts agree with the IPCC on its fundamental assertions, as indicated by the US National Academy of Sciences (NAS) support for the June 2005 joint declaration.
The Union of Concerned Scientists' website has an excellent summary of the "skeptic" organizations, their tactics, and other hoaxes such as the Leipzig Declaration.
More recently, some climate change skeptics have cited the UK Channel 4 program entitled, "The Great Global Warming Swindle", originally broadcast in March 2007, as evidence that climate scientists are misleading the public.
The program argues that cycles of increased solar activity and interaction with cosmic rays rather than human activity, are the principle cause of global warming (and that the record of solar activity matches temperature changes over the past 100 years). However, a scientific paper published in Proceedings of the Royal Society A in July 2007 (Lockwood and Frohlich) indicates that the Sun's output for the last 20 years has actually declined while temperatures on Earth have risen.
The Lockwood/Frohlich study concludes that modern temperatures are not determined by the Sun's effect on cosmic rays. One of the authors of the study, Professor Mike Lockwood, also specifically criticized the Channel 4 program for selective methodology and omitting data that didn't support the program's main arguments. Since the Channel 4 program originally aired, two of the scientist who participated have complained that their views were misrepresented. Over 35 scientists have also complained to a UK broadcasting watchdog that the program breached the broadcasting code by misrepresenting views and facts.
Are current climate changes within natural variability?
Using indirect measures from sources such as ice cores from the poles and tree rings from ancient forests, scientists can make excellent guesses about the baseline temperature trends.
When scientists review such data they conclude that the average global temperature has most likely never been this high for at least 1000 years and the atmospheric concentration of the greenhouse gas CO
2 has not been this high for 420,000 years and likely never this high over 20 million years.
The 'all within variation' notion is countered in part when viewing the following IPCC graph, below. There was a slight downward trend in average global temperature until the early 1900's at which point there was a massive upswing. The present level (in red) is higher than the 95% error or uncertainty range depicted in grey. This error is larger prior to the thermometer data in red at which point it becomes much less broad. The rate of average temperature increase in the last century is unprecedented in the past 1000 years.
Departures in temperature (top measurements)
1000 years. Departures in temperature (left-hand side measurements)
Source: IPCC, Working group I, Summary for Policy Makers (SPM), Third Assessment Report (TAR), page 3.
Impacts on Canada
Unfortunately for Canadians, the effects of climate changes are predicted to be greater in our region of the world. While global average temperatures, for example, should rise by 2 to 6 degrees Celsius by the end of the century the Canadian average will be within the 6 to 10 degree range.
Already in Canada's north, the Inuit are seeing robins - a bird for which their ancient language has no word. Residents of Sachs Harbour on Banks Island have seen the permafrost melt and witnessed an unprecedented event - a thunder and lightening storm. The ice is thinning, as are the polar bears.
In the last few years, the federal government has spent billions of dollars in response to extreme climate variations such as drought. The B.C. government expects infestations of the spruce pine beetle to increase in severity and frequency due to warmer winters. The 5000 to 16000 annual smog related deaths in Canada will only increase with more heat. The list of existing and worsening problems goes on.
Won't a few degrees more be good for the plants?
When Canadians hear the range of predicted temperature increases as a result of climate change, they sometimes react by saying, "A few degrees...that's it? I'd love it to be a few degrees warmer on average!"
Most don't realize that this is a global average (as noted, it will likely be higher in Canada) and that small changes in the global temperature average can bring about huge effects. The last ice age, for example, was only, on average, about 5 degrees Celsius cooler than today. If that little cooling could result in such drastic effects, what could happen with a much more rapid shift in temperature?
It's also tempting to think that an increase in CO2 will help plants as they use CO2 to grow and higher temperatures mean longer growing seasons. However, one needs more than temperature and CO2 to successfully grow a plant. The other key ingredients are, of course, sunlight and water.
The water cycle will be drastically altered with increased temperatures, increasing the number and severity of both droughts and floods. Higher temperatures increase the rates of evaporation from the surface. When conditions momentarily shift, the massive amounts of water now held in the atmosphere flow down in torrential quantities. Unfortunately, the prairies are already seeing this new pattern emerge. What good is a longer growing season, if it's just longer drought?
It's a dismal surprise for many to find out that sunlight reaching the earth's surface will also be altered. Global increases in temperature will likely increase ozone layer depletion - bringing about more plant-damaging UV rays.
Other impacts of temperature increases include the possibility of more insect infestations, because larvae will better survive through winters, and an increase in the frequency and severity of fires.
How do the scientific models project future trends?
Because it's impossible to do traditional science on the entire atmosphere (you can't, for example, manipulate one variable and see how all the others change and then jump in a time machine and re-run the experiment a few times) scientists are left with computer simulations that rely on using the well established scientific equations describing the atmosphere and oceans.
The main way that scientists test the validity of their computer models is to determine how the models do at matching past temperature patterns. The following graph shows the match between observed data for 140 years and what the model would have arrived at. This model, cited by the IPCC working group I, incorporates a wide range of factors including natural (volcanoes, solar radiation changes, etc.) and human induced variables (fuel burning, deforestation, etc.). As indicated on the chart, the model is far more 'on' than 'off' at trying to capture the pattern.
Temperature anomalies
Source: IPCC, Working group I, Summary for Policy Makers (SPM), Third Assessment Report (TAR), page 11.
Carbon Dioxide levels and temperature
CO2, like all greenhouse gases, has the general effect of heating up the atmosphere. There are times where temperature and gas concentrations don't move up or down in perfect synchrony because CO2 is just one of many factors to influence the world's temperature. Overall however, the idea is that generally the more you put in the sky, the warmer it gets and this is well supported by evidence.
The following chart, originally published in the scientific journal Nature, is notable for two things. One is that CO2 exists in very small or trace concentrations (ppmv = parts per million by volume). Remarkably, CO2 influences temperature despite existing only in trace amounts.
The other thing you will notice is that "present" means 1950. Since 1950, the levels of CO2 in the atmosphere have gone up to about 375 ppmv - completely off this chart which goes back 420,000 years. The upper line has since continued well up to the right.
Temperature-CO2 concentration
Source: GRID (Global Resource Information Database of the United Nations Environment Program in Arendal, Norway)
Human activity vs. solar radiation in climate change
According to past IPCC findings, the warming effect due to increases of greenhouse gases in the atmosphere was estimated to be more than 8 times greater than the effect of solar irradiance changes. That estimate was revised upward in the 2007 IPCC review - the warming effect due to greenhouse gases is now set at a level 13 times greater.
Radiative Forcing
Source: GRID
This page contains excerpts from an earlier report prepared for the Sierra Club of Canada: Ten Popular Myths About Global Climate Change
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August 2008 
Inukshuk
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