Transcript Document

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
The IPCC has provided sound science advice on
climate change for more than a decade
Cautious
1990
First Report
1992
1995
Second Report
1997
Increasing
Confidence
2001
Third Report
Are the IPCC results credible?
US National Academy of Science 2001
report to President Bush
The most recent IPCC assessment is…“an admirable
summary of research activities in climate science”
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
Suitable, stable
climate
and weather
Protection from solar uv-b
(stratospheric ozone)
stratosphere
surface
troposphere
The air we breath
(21% oxygen)
thunderstorm
Outgoing
Heat Energy
Incoming
Solar Energy
Reflected Energy
~31%
Energy Trapped
By Greenhouse Gases
•CO2
0.028%
•CH4
0.0007%
•N2O
0.0003%
Current greenhouse gas concentrations are
unprecedented in at least the past 400,000
years
380
CO2 Concentration (ppmv)
360
340
$
320
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Highest concentration in last 400,000 years
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260
900
1000
1100 1200 1300 1400 1500 1600 1700 1800 1900 2000
Global surface temperatures are
rising
1860-2001
Degrees C
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
1860
1880
1900
1920
1940
Year
1960
1980
2000
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
-15
-20
2090s
-25
2050s
-30
-35
-40
1980s
CGCM1 results suggest very hot days across
Canada will become much hotter…
40
2090s
35
2050s
1980s
30
25
The frequency and severity of droughts are also
likely to increase in southern Canada
Central North America
40
20
~2070
0
Return Period (years)
60
Today
10
15
20
25
Length of Dry Spell (days)
30
…while extreme precipitation events are likely to
become more frequent
Size of event (mm)
Extreme Precipitation Events (Canada)
95
90
85
80
75
70
65
60
55
50
2090
2050
1985
10
20
30
40
50
60
70
Event recurrence time (Years)
80
Extreme events can cause many types of disasters
Lightning damage
Flood
losses
Wind
damage
Ecological
disaster
Loss of
life
Structural
damage