Climate Projections

Question 1

1. Recent Global Warming

How much has global mean temperatures risen since 1880?

Answer 1

Global mean temperatures have risen by 0.65-1.06 0C since 1880.

Question 2

1. Recent Global Warming

Temperatures after 1980…

Answer 2

Temperatures after 1980 have been higher than at any time in the last 10 000 years.
2011-2015 is the warmest five year period with 2015 the warmest year on record.

Question 3

1. Recent Global Warming

Ocean temperatures

Answer 3

Mean ocean temperatures highest on record.

The rise parallels the 20th /21st centuries’ rise in atmospheric CO2 concentrations, the main greenhouse gas

Question 4

1. Recent Global Warming

CO2 levels

Answer 4

At ~400 ppm, CO2 levels are higher than anytime in last 850 000 years
The early-mid 20th C rise partly parallels increased solar irradiation (sunspots)

Question 5

1. Recent Global Warming

Difference between latitudes

Answer 5

High latitudes have warmed the most

Question 6

Changes in precipitation 1901-2010

Answer 6

Over the 20th century several regions became
wetter.
Since 1950s more regions becoming drier.

Question 7

Changes in extreme events?

Answer 7

No. of cold days and nights decreased and no. of warm days and nights increased on the global scale.

Frequency of heat waves increased in large parts of Europe, Asia and Australia.

More land regions where the no. of heavy precipitation events has increased than where it has decreased.

Frequency or intensity of heavy precipitation events increased in North America and Europe.

Question 8

2. Global Climate Models (GCMs)

Answer 8

Based on mathematical representations of laws of physics and chemistry.
Based on 3D system of cells from earth’s surface to upper
atmosphere.
Models simulate movements of energy and matter in horizontal and vertical directions: hence simulate atmospheric conditions/climate.
Models simulate climate over decades into the future on a surface grid basis typically ~100 x 100 km.
Allows for simulation of interactions between terrestrial, marine and atmospheric and some of the feedbacks.

Question 9

3. Global Climate Projections

Answer 9

Forward projections - for different RCPs
Trends shown are averages of several major GCMs run in
different countries (eg. UK Met Office Hadley Centre)
‘Ensembles’ of runs with slightly different setups give
estimates of uncertainties (minimum-maximum ranges)
Mean annual/monthly temperature and precipitation
Often expressed as units, % or fractional anomalies from a pre-determined baseline eg. 1980-1999 mean.

Question 10

4. UK Climate Changes

Answer 10

UK Climate Impacts Programme (UKCIP) based at
Oxford University with Met Office Hadley Centre, Exeter
Low, medium and high emission scenarios
Latest projections 2009
Higher resolution than GCMs
Coupled to ‘weather forecasting’ model at ~10km x 10km

Question 11

5. Feedbacks and Surprises

Answer 11

Warm climate is melting Arctic Sea ice so increasing size of ‘dark coloured’ heat-absorbing sea –positive feedback

Warm climate may increase rate of permafrost melting so increasing release of methane – positive feedback

Warm climate and more forest may reduce reflectance properties (albedo) and increase surface warming - positive feedback

Warmer atmosphere may accelerate melting of ice-caps and glaciers -could lead to disruption of North Atlantic Thermohaline Circulation and Gulf Stream leading to colder Europe – negative feedback