Information and background on climate change

Gustav StrandbergRossby Centre, SMHI, Sweden

090401

Climate has always been changing

Carbon dioxide”Temperature”Interglacials

600 500 400 300 200 100 0 Years*1000 before 2005

(IPCC, 2007)

Global emissions of carbon dioxide increases the

amount in the atmosphere

Temperature change – global and in Sweden

(compared with the years 1961-1990)

The concentration of CO2 in the atmosphere has reached a record high relative to more than the past half-million years, and has done so at an exceptionally fast rate. Current global temperatures are warmer than they have ever been during at least the past five centuries, probably even for more than a millennium. If warming continues unabated, the resulting climate change within this century would be extremely unusual in geological terms.

IPCC, 2007

Radiation components: change 1750 to 2000

(IPCC, 2007)

The present climate change can not be explained without anthropogenic effects

(IPCC, 2001)

Given certain CO2-emissions what will future concentrations be?

2008 386 ppmv2007 10 Gt C / yr

Emission scenario + global climate model + (regional climate model) + time period = climate scenario (or climate projection)A climate scenario is a combination of several assumptions.

Uncertainties in the i scenario

• What we don’t know. Future amounts of green-house gases.

• What we can’t describe. Different climate models represents the climate system differently and with different quality.

• Natural variability. A climate model can not exactly reproduce the climate in one specific year.

Scenarios are not forecasts Climate models does not

reproduce the real weather in a specific point at a certain time. A good quality climate model gives a probable realisation of the weather, with realistic statistical properties.

Climate models

(NCAR)

Climate model: Three dimensional representation of the atmosphere coupled to the land surface and oceans (biosphere, carbon cycle, atmosphere chemistry)

Global resolution100 – 400 km

Regional resolution10 – 50 km

Resolution in different models

Global Regional

How good is a climate model?

Observations, models, model mean

How can a climate model say something about what happens in 100 years, when a weather prediction can not be longer than one week?

The atmosphere is like a non-linear equation: X=A*X – X2

Future temperature according to different scenarios

Climate change is different in different regions

• Precipitation increases in some areas and decreases in others

°C per +1°C in global average temp.

% per +1°C in global average temp.

• Some regions will be more heated than others

Future global warming – despite uncertainties there are clear signals

Climate change presentation – Example Sweden

http://www.smhi.se/cmp/jsp/polopoly.jsp?d=8785&l=sv

The analysisTwo scenarios: SRES A2, SRES B2Global model: ECHAM4/OPYC3Regional model: RCA3

Sweden is divided into regions. All grid boxes that fall into a region are collected. For each region time series and statistics are calculated.

Results

ResultsTime series – annual and seasonal

AnnualA2B2

SeasonalWinterSpringSummerAutumn

A2 B2

ResultsFrequency distributions 1961-1990, 2071-2100

A2 B2

Winter

Summer