Thank you very much, Mr. Chairman.
Chairman and members of this legislative committee, I'm grateful for the opportunity to appear before you today to share with you some of the main conclusions of the recently completed report of the Intergovernmental Panel on Climate Change's Working Group I on the physical science basis of climate change.
First, I have some general comments.
With this report, the debate on the science of climate change is effectively over. There can no longer be any question that the climate is changing. According to this report, warming of the climate system is now unequivocal. According to the Oxford English Dictionary definition, this implies that the science is now unambiguous.
Furthermore, most of the observed increase in globally averaged temperatures since the 1950s is, it is now very likely, due to human activities that have given rise to increases in atmospheric greenhouse gas concentrations. “Very likely”, in the words of the IPCC, means at least a 90% certainty. Scientific results don't often get as clear as that.
The IPCC report is authoritative and well balanced and reflects peer-reviewed work of thousands of scientists around the world. As an assessment, however, it treats new results with caution and is therefore somewhat conservative.
My own reading of the literature suggests that the climate change is actually speeding up and that the trends are no longer simply linear. In my view, this suggests an urgency to addressing the issue of climate change. There is, indeed, a growing body of literature that suggests that the longer we delay tackling the threat of climate change, the greater will be the risks and the greater will be the potential costs.
Let me talk a little bit about what we have observed, and first about the root cause of the threat; that is, the changes we have made to the composition of the atmosphere mainly by the burning of fossil fuels.
The atmospheric concentration of carbon dioxide in 2005 exceeds by far the natural range over the last 650,000 years. That is over some six or seven ice ages. In short, we have taken the atmosphere into unknown territory.
More worrying is that the annual growth rate of carbon dioxide concentration is now larger than it has been since continuous records were begun in about 1960, and that is consistent with the continued growth in emissions. We are clearly far from stabilizing, let alone reversing, the root cause of the problem.
We know from well-established physics that increasing the concentrations of greenhouse gases in the atmosphere will affect the climate, and indeed, that is what has been observed. Eleven of the last twelve years are among the warmest in the instrumental record, roughly since 1850, and the linear trend in warming continues to increase.
Global average temperatures have increased by almost three-quarters of a degree over the past 100 years. We now have evidence that the oceans also have warmed and in fact have taken up almost 80% of the heat added to the climate system, which has resulted in temperature increases down as far as three kilometres. This heat in the oceans will take centuries to work itself through the climate system.
Global average temperatures are now higher than at any time in the last 1,300 years, and projected patterns of warming would continue these recent trends. It is extremely unlikely that observed changes over the past 50 years can be explained without invoking the increases in greenhouse gas concentrations in the atmosphere.
In addition, average Arctic temperatures have increased at twice the global average rate over the last 100 years, and Arctic sea ice extent has declined by almost 3% per decade, with much larger decreases in the summer, and there are signs that these rates of decline are in fact increasing.
More intense and longer droughts have been observed over wider areas since the 1970s. At the same time, the frequency of heavy precipitation events has increased. There is observational evidence for an increase in the most intense hurricanes in the North Atlantic since about 1970. Outside the Tropics, mid-latitude westerly winds—the sorts of winds that hit the west coast in December—have strengthened in both hemispheres since the 1960s. That's what we've observed.
As for the future, over the next two decades, at least, further global temperature increases of 0.1 degrees Celsius per decade are in fact inevitable because of what we've already done to the atmosphere. All scenarios of future emissions project that the warming could in fact be twice as large as that. Best estimates of temperature increases by the end of the century range from 1.8 degrees to 4 degrees Celsius, with a forecast sea level rise from roughly 0.2 to 0.6 metres. In addition, snow cover and sea ice are expected to contract, with the possibility that arctic sea ice will be almost entirely absent in summer. Hence, there will no longer be multi-year ice by the latter half of the century. Weather and climate extremes, including heat waves, droughts, heavy precipitation, and winds will continue to become more severe and frequent.
Recent observations of unexpected acceleration in the flow speeds of out-lake glaciers from Greenland and Antarctica, from the ice sheets there, have led scientists to recalibrate their understanding of glacier physics. Contraction of the Greenland ice sheet is projected to indeed continue to contribute to sea level rise.
Current models suggest that ice mass losses increase faster than gains due to more precipitation if the global average temperatures are greater than 1.9 degrees Celsius above pre-industrial levels. I may note that we're almost halfway there. If sustained for several millennia, the ice sheet would completely disappear, with a sea level rise in the order of seven metres. We haven't seen such sea level rise since the last interglacial period some 125,000 years ago.
To conclude, as I suggested, with this report, the debate on the science of climate change is effectively over. We now have to focus on solutions before it's too late. This will be the subject of the next two IPCC working group reports.
Thank you, Mr. Chairman.