The Science Behind The Science Behind

The Climate Change The Climate Change Issue Issue

Henry HengeveldMeteorological Service of CanadaEnvironment 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

1990

1992

1995

1997

2001

First ReportFirst Report

Second ReportSecond Report

Third ReportThird 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 Sciencefrom 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

thunderstormtroposphere

The air we breath (21% oxygen)

Suitable, stable climate

and weather

     

                       

 

 

Reflected Energy~31%

Incoming Solar Energy

Outgoing Heat Energy

Energy TrappedBy 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

Highest concentration in last 400,000 yearsHighest concentration in last 400,000 years

900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000260

280

300

320

340

360

380

CO

2 C

once

ntra

tion

(ppm

v)

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 There is new and stronger evidence that most of the evidence that most of the

warming observed over the warming observed over the last 50 years is attributable to last 50 years is attributable to

human activities. ”human activities. ”

Intergovernmental Panel on Climate Change 2001Intergovernmental Panel on Climate Change 2001

The world will MUCH, MUCH warmerThe world will MUCH, MUCH warmer

Projected temperature changes vary considerably from year to year

Changes in precipitation patterns by 2050 areuncertain, but will be complex

Extreme cold days will become much less cold

1980s

2050s

2090s

On

e in

te n

yea

r e x

trem

e (º

C )

CGCM1 results suggest very hot days across Canada will become much hotter…

1980s

2050s

2090s

On

e in

te n

yea

r e x

trem

e (º

C )

The frequency and severity of droughts are also likely to increase in southern Canada

020

40

60

Retu

rn P

eri

od (

years

)

10 15 20 25 30

Length of Dry Spell (days)

Central North America

Today

~2070

…while extreme precipitation events are likely to become more frequent

95

50

55

60

65

70

75

80

85

90

Event recurrence time (Years)

Siz

e of

eve

nt

(mm

)

10 20 40 8030 50 60 70

1985

2050

2090

Extreme Precipitation Events (Canada)

Extreme events can cause many types of disasters

Lightning damage

Floodlosses

Ecologicaldisaster

Structural damage

Wind damage

Loss oflife