Climate scientists and government officials gathered in Brussels, Belgium on April 6 to issue the second of four reports about climate change.

The Intergovernmental Panel on Climate Change (IPCC) released its summary for policy makers on Feb. 2. Climate Change 2007: The Physical Science Basis found that human activity, primarily the burning of fossil fuels, is driving climate change.

This report is entitled "Impacts, adaptation and vulnerability." The UN-sponsored body last reported on this topic in 2001.

This report has more specifics than six years ago -- how climate change will affect the planet and how humanity must think about adapting to it. 

The impact on Canada

Various media outlets obtained copies of a technical report that looked specifically at North America.

Here are some of the findings:

• Snowmobiling might become a thing of the past in eastern Canada by 2050.
• Ski seasons could become significantly constricted in Western Canada.
• Pacific salmon are starting to show up in Arctic rivers because their traditional spawning rivers are getting too warm.
• "Severe heat waves, characterized by stagnant, warm air masses and consecutive nights with high minimum temperatures, are likely to intensify in magnitude and duration over portions of the U.S. and Canada, where they already occur," the scientists say. The elderly and urban poor will likely bear the brunt of such heat waves.
• Smog deaths will rise about five per cent by 2050 in cities with existing smog problems.
• The range of ticks carrying Lyme Disease could spread northward in Canada
• Allergic pollen problems will become more acute
• By 2100, forest fires are expected to destroy about double the forest area they currently harm. Forests in Canada are carbon sinks, but the Toronto Star reported on April 4 that the federal government is worried that forests could soon become a net contributor to greenhouse gas emissions.
• About one-fifth of the "Arctic desert" -- an area of permafrost and minimal precipitation -- will convert to green tundra. About one-third of the permafrost will be gone by mid-century.
• Great Lakes water levels will drop, as might other major river systems. This could affect navigation, hydro power generation and water quality.
• Warmer temperatures could affect precipitation patterns in the Rocky Mountains. There is likely to be more winter flooding and lower summer flows in rivers originating there.

These effects are described as likely.

Certainty and the report

The summary represents the consensus opinion of about 120 national governments, based on the world of about 2,000 scientists who have reviewed the world's climate change research.

Findings are described in terms of likelihood:

• Virtually certain - More than 99 per cent probability of occurrence,
• Extremely likely - More than 95 per cent,
• Very likely - More than 90 per cent,
• Likely - More than 66 per cent,
• More likely than not - More than 50 per cent,
• Unlikely - Less than 33 per cent,
• Very unlikely - Less than 10 per cent, and
• Extremely unlikely - Less than 5 per cent.

Possible positive impacts for Canada

• Polar sea ice, already shrinking, may retreat by another 22 to 33 per cent by century's end, allowing navigation of the Arctic Ocean.
• Longer growing seasons could boost crop production for a few decades. However, insect infestations will also increase.
• Forests might also show faster growth, but that will be offset in the second half of the century by increased fire activity.

Global impacts

"Observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases," said the summary.

"A global assessment of data since 1970 has shown it is likely that anthropogenic warming has had a discernible influence on many physical and biological systems."

• Spring is arriving about two weeks earlier than normal in the northern hemisphere.
• Global warming can be blamed for the extinction of about 70 species so far. About 20 to 30 per cent of the world's species could face extinction by 2050. There are an estimated 1.75 million discovered species on Earth, says the Science and Development Network.
• One "glamour species" under threat are polar bears. The U.S. government is considering listing polar bears as a threatened species because of the impact of climate change on their habitat. The Washington Post reported in late December that this is the first time the Bush administration has identified a species being put at risk because of climate change.
• Warmer water is killing tropical coral reefs. The animals that build the coral become stressed by the heat. They spit out the algae that gives coral its colour. Because the oceans absorb carbon dioxide from the atmosphere, this will make the seas more acidic. That will reduce the ability of coral to build reef skeletons.
• Freshwater supply is a major concern. An estimated 400 million to 1.7 billion people will not have enough water by 2020. By 2050, up to two billion people will face water shortages. The world currently has 6.5 billion people, but that is expected to rise to nine billion by 2050.
• Slowly rising sea levels will threaten coastal and low-lying countries.
• Rich, northern-hemisphere countries will be hurt less by climate change than poor, southern-hemisphere ones, which will see food production drop. "Like the sinking of the Titanic, catastrophes are not democratic," Henry I. Miller, a fellow with the Hoover Institution at Stanford University, told the New York Times on April 1. "A much higher fraction of passengers from the cheaper decks were lost. We'll see the same phenomenon with global warming."

How bad can it get?

That largely depends on humanity's collective response to the climate change crisis.

A rise of two degrees or less will change the world's climate patterns but should be manageable.

Any increase above that, however, and the impacts become progressively more severe. The high end of the range given in the Feb. 2 report was 6.4 degrees by 2100, which experts say would be catastrophic.

"The worst stuff is not going to happen because we can't be that stupid," Harvard University oceanographer James McCarthy, an author of the 2001 version of the impacts report, told The Associated Press. "Not that I think the projections aren't that good, but because we can't be that stupid."

The Global Legislators Organisation for a Balanced Environment  (GLOBE) -- which includes the G8 countries plus China, India and Brazil -- set a target this winter of  stabilizing global CO2-equivalent levels at 450 to 550 parts per million, which would hopefully keep the temperature rise below two degrees. The current level is 380 parts per million and rising. They want the G8 to adopt that target for "Kyoto II" -- the replacement for the Kyoto Protocol, the current climate change-fighting treaty that expires in 2012.

The controversy

The summary is written by government officials and represents a consensus view of those participating governments.

However, there were significant tensions reported between scientists and those officials.

Many scientists report that China, poised to become the world's biggest net greenhouse gas emitter (Canada and the U.S. emit far more on a per capita basis), pushed hard to weaken the summary's language. Saudi Arabia, one of the world's biggest oil producers, also pushed for weaker language.

Some scientists said they wouldn't participate in the IPCC process in the future, but others said even the toned-down report sent a strong message.

"This is a glimpse into an apocalyptic future. The earth will be transformed by human-induced climate change unless action is taken soon and fast," said Stephanie Tunmore, Greenpeace International Climate and Energy Campaigner.

"What this report shows is that we are simply running out of time."

Sources: CTV, IPCC, the Toronto Star, the Associated Press, The Globe and Mail, the New York Times, Science and Development Network, Greenpeace International