Scientists first started theorizing about human activity impacting climate change in the early 1960s.

The first major international meeting on climate change took place in 1979.  Delegates issued a statement expressing concern that "continued expansion of man's activities on earth may cause significant extended regional and even global changes of climate."

While there was talk of a new global body to address this threat, the wheels of international organizations turn slowly.

In 1985, another international conference found that "as a result of the increasing greenhouse gases it is now believed that in the first half of the next century (21st century) a rise of global mean temperature could occur which is greater than in any man's history."

Two years later, there was agreement that a new organization was needed to monitor this emerging threat.

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:

• "The role of the IPCC is to assess on a comprehensive, objective, open and transparent basis the scientific, technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change, its potential impacts and options for adaptation and mitigation."

What doesn't it do?

Again, from the website:

• "The IPCC does not carry out research nor does it monitor climate related data or other relevant parameters. It bases its assessment mainly on peer reviewed and published scientific/technical literature. Its role, organisation, participation and general procedures are laid down in the 'Principles Governing IPCC Work'."

Who's involved?

Climate change experts from all over the world and 154 countries plus relevant non-governmental organizations (NGOs).

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.

They meet once a year and table an assessment every five or six years. The IPCC released its first assessment in 1990. It released subsequent ones in 1995 and 2001.

What was contained in the assessment?

The first part of the fourth assessment dealt with the scientific basis for the theory that climate change is actually occurring.

However, three other parts will be released over the course of the year. They will include areas like the impact of climate change, how it can be mitigated and greenhouse gas inventories. Observers are particularly looking forward to the report on the impact of change.

When was it released?

On Friday, Feb. 2 in Paris, France.

Was the whole report released?

No. A policy-maker's summary was made public on that date. The entire report first section won't be released for months

Who wrote that summary?

A team of government officials working in secret. They worked from the main report (a draft was released last spring). Their names are listed on the report.

Who wrote the main report?

A global team of 600 scientists. Another 600 scientists reviewed what they wrote. Each member government had a chance to respond and suggest revisions.

What was it expected to 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.

The Associated Press reported the following excerpts from earlier drafts in a Jan. 22 story:

• "Observations of coherent warming in the global atmosphere, in the ocean, and in snow and ice now provide stronger joint evidence of warming," and
• "An increasing body of evidence suggests a discernible human influence on other aspects of climate including sea ice, heat waves and other extremes, circulation, storm tracks and precipitation."

That seems like cautious language. Is there a reason?

The IPCC is a cautious group.

"In a way, it is one of the strengths of the IPCC to be very conservative and cautious and not overstate any climate change risk," said Stefan Rahmstorf, a physics and oceanography professor at Potsdam University in Germany, in a Jan. 28 AP story.

What's the main controversy right now?

Some experts have accused the IPCC of "sugarcoating" the assessment by not taking into account the melt-off of two major ice sheets in Greenland and Antarctica.

By doing so, the assessment is "obviously not the full story because ice sheet decay is something we cannot model right now, but we know it's happening," Rahmstorf said.

Another excerpt from the Jan. 28 AP story:

• "Those scientists who say sea level will rise even more are battling a consensus-building structure that routinely issues scientifically cautious global warming reports, scientists say. The IPCC reports have to be unanimous, approved by 154 governments -- including the United States and oil-rich countries such as Saudi Arabia -- and already published peer-reviewed research done before mid-2006."

What are some of the main findings?

The early assessments were correct. 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.

"Extremely likely" means more than a 95 per cent chance, and "virtually certain" is more than 99 per cent. In the 2001 report, scientists said human influence was likely the reason, which mean more than a 66 per cent chance.

The report found that 11 of the last 12 years have been among the warmest based on global surface temperature since 1850. The report found that 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.

However, there were some anomalies. For example, the report found that Antarctic sea ice has shown no statistically significant changes.

The IPCC expects warming of about 0.2 degrees Celsius  per decade. 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, that 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," the report said.

One sobering finding is that 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. "The magnitude of this feedback is uncertain," the report said.

On balance, the report 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 happens now that the report has been released?

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 country's are trying to establish the framework for "Kyoto II," a new treaty to replace Kyoto, which expires in 2012.

What individual countries will do in response is an open question. However, because it's a consensus report, countries that participated -- which includes Canada -- are essentially saying they agree with its assertion that climate change is happening and that human activity is driving it.

Sources: The IPCC, the Associated Press and files from CTV News' David Akin