Scientists first started theorizing about human activity impacting climate change in the early 1960s, and the first major international meeting on climate change took place in 1979.
In 1985, another international conference found that increasing greenhouse gases could mean a rise of average global temperature greater than any in man's history. Three years later, the Intergovernmental Panel on Climate Change was founded to monitor the emerging threat. Here are some answers about the global authority on climate change:
What is the Intergovernmental Panel on Climate Change (IPCC)?
The United Nations Environment Program and the World Meteorological Program created the IPCC in 1988.
From the IPCC website:
It's role is to assess the scientific, technical and socio-economic information relevant to understanding the risk of human-induced climate change, its potential impacts and options for adapting and mitigating the changes.
What doesn't it do?
It doesn't carry out research or monitor climate related data. It bases its assessment mainly on peer reviewed and published scientific papers.
Who's involved?
Climate change experts from 154 countries plus non-governmental organizations.
Several Canadian scientists have played and continue to play leading roles within the IPCC, including Dr. Andrew Weaver of the University of Victoria and Dr. Gordon McBean of the University of Western Ontario.
The IPCC meets once a year and have released an assessment every five or six years since 1990.
What is contained in the assessments?
The first part of the assessment deals with the scientific basis for the theory that climate change is actually happening.
Three other parts include the impact of climate change, how it can be mitigated and greenhouse gas inventories.
Who wrote the latest report?
A global team of 600 scientists. Another 600 scientists review what they wrote. Each member government had a chance to respond and suggest revisions.
What does the latest report say?
That human-influenced climate change is indeed happening, that it can't be explained away as a natural phenomenon -- and that is destined to get much worse in the future.
Humans influence other aspects of climate including sea ice, heat waves, circulation, storm tracks and precipitation.
Why is the report worded so cautiously?
The IPCC is a cautious group. Some experts say it's a good thing the IPCC is very conservative and cautious and not overstate any climate change risk. Making predictions that prove to be false could damage the organization's reputation as legitimate.
What's the main controversy surrounding the report?
Other experts have accused the IPCC of sugarcoating the assessment by not taking the melt-off of two major ice sheets in Greenland and Antarctica into account in the report. They say the predictions would be much worse if the ice sheets were factored in, so the assessment doesn't provide an accurate picture.
What are some of the last report's main findings?
The report finds that the climate is warming, and that human influences are "very likely" to have caused that.
To put the "very likely" into context, that means scientists think human influence is more than 90 per cent likely to be causing global warming and the resultant climate change that we are seeing.
This evidence and impacts include:
- Eleven of the last 12 years have been among the warmest based on global surface temperature since 1850. Atmospheric and ocean temperatures have also increased;
- Mountain glaciers and snow pack have declined in size in both hemispheres. The permafrost zone is shrinking. Sea levels are rising. Heat waves are increasing in intensity and frequency;
- Warming of about 0.2 degrees Celsius per decade is expected. If greenhouse gas emissions were held at 2000 levels, the report predicted temperatures would still rise 0.1 degrees per decade;
- If greenhouse gas emissions continue at or above current rates, it would likely drive changes that were greater than what was seen during the 20th century.
- The probable temperature rise by the end of the 21st century will be between 1.8 and 4 degrees. The possible range is 1.1 degrees to 6.4 degrees. Sea levels will go up by 28 to 43 centimetres;
- It is very likely that hot extremes, heat waves, and heavy precipitation events will continue to become more frequent;
- Even if greenhouse gas emissions are stabilized, global warming will continue because of "feedback." For example, ice sheets reflect the sun's energy. As ice disappears, that means more of the sun's energy is absorbed by the earth and radiated into the atmosphere;
- Teport found that past and future human-caused greenhouse gas emissions will contribute to global warming for at least a millenium, due to the time required for these gases to disappear from the atmosphere.
What impact do the reports have?
Policy-makers hopefully use the report to guide their decision-making.
The 1990 report led to the United Nations Framework on climate Change. The 1995 report was used in negotiations for the Kyoto Protocols on fighting climate change.
This report comes out as the world's countries are trying to establish the framework for "Kyoto II," a new treaty to replace Kyoto, which expires in 2012.
Because it's a consensus report, countries that participated - including Canada -- are essentially saying they agree with its assertion that climate change is happening and that human activity is driving it.
