The Science Behind The Climate Change Issue Henry Hengeveld Meteorological Service of Canada Environment Canada

Climate change science is complex science Involves many different disciplines Has benefited from several decades of intensive research –Globally, several thousand papers currently published each year, at an annual cost of ~$US 3 billion Like a huge jigsaw puzzle having 10s of thousands of pieces Requires comprehensive international effort involving experts from all disciplines involved to properly assess

Cautious Increasing Confidence The IPCC has provided sound science advice on climate change for more than a decade First Report Second Report Third Report

Are the IPCC results credible? The most recent IPCC assessment is…“an admirable summary of research activities in climate science” US National Academy of Science 2001 report to President Bush Joint statement by Academies of Science from 17 other countries – May 2001 “The work of the…IPCC represents the consensus of the international science community on climate change science. We recognize IPCC as the world’s most reliable source of information…and endorse its method of achieving this consensus.”

The earth’s atmosphere provides several important life supporting services Protection from solar uv-b (stratospheric ozone) surface stratosphere thunderstorm troposphere The air we breath (21% oxygen) Suitable, stable climate and weather

Reflected Energy ~31% Incoming Solar Energy Outgoing Heat Energy Energy Trapped By Greenhouse Gases CO20.028% CH % N2O0.0003%

Current greenhouse gas concentrations are unprecedented in at least the past 400,000 years Highest concentration in last 400,000 years

Global surface temperatures are rising

Modelled response to natural forcings differs from observed temperatures during past 50 years

Modelled response to all forcings agrees best with observations

Current NH temperatures are very unusual within at least the past 1000 years

The physical world is dramatically changing Receding glaciers Retreating Arctic sea ice Rising seas

“ There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities. ” Intergovernmental Panel on Climate Change 2001

The world will MUCH, MUCH warmer

Projected temperature changes vary considerably from year to year

Changes in precipitation patterns by 2050 are uncertain, but will be complex

Extreme cold days will become much less cold 1980s 2050s 2090s One in ten year extreme (ºC )

CGCM1 results suggest very hot days across Canada will become much hotter… 1980s 2050s 2090s One in ten year extreme (ºC )

The frequency and severity of droughts are also likely to increase in southern Canada Return Period (years) Length of Dry Spell (days) Central North America Today ~2070

…while extreme precipitation events are likely to become more frequent Event recurrence time (Years) Size of event (mm) Extreme Precipitation Events (Canada)

Extreme events can cause many types of disasters Lightning damage Flood losses Ecological disaster Structural damage Wind damage Loss of life