Emissions of greehhouse gasses

Climate forcing factors

=

Factors causing climate to change

Temperature

• Direct temperature measurements span 140 years

• Global temperature has increased about 1 deg C

Greenhouse gases

Earth

Sun

Atmosphere

Some infrared radiation is absorbed by greenhouse gases warming Earth and lower atmosphere

Some solar radiation is reflected by atmosphere

More radiation is absorbed by Earth and

warms it

Infrared radiation (heat) is released from the

Earth

Greenhouse gasesGreenhouse warming potential (GWP) -- takes into

account the ability of a gas to absorb infrared radiation, and the lifetime of the gas in the atmosphere

Gas [conc] GWPcarbon dioxide (CO2) 360 ppm 1

methane (CH4) 1745 ppb 23

nitrous oxide (N2O) 314 ppb 296CFC-11 268 ppt 4600

CFC-13 4 ppt 14000

water (H2O)

A diversion to the stratosphere…

These gases affect the ozone layer in the stratosphere (GOOD OZONE)

BUT

this is not related to their effect as a greenhouse gas in the troposphere (BAD OZONE)

CFC’s:

Stratosphere

Troposphere

Earth

0 to 10 km

10 to 45 km

A diversion to the stratosphere…

Good ozone

Bad ozone

Ozone

• Good ozone shields the earth from UV radiation

Ozone

• Good ozone shields the earth from UV radiation

• Bad ozone = smog; affects animal and plant health

Ozone

• Good ozone shields the earth from UV radiation

• Bad ozone = smog; affects animal and plant health

Neither are climate forcing factors!

Back to greenhouse gasses and climate forcing…

Greenhouse gases

Carbon dioxide is the largest single contributor to climate forcing

Carbon dioxide contributes about half of total climate forcing from greenhouse gases

Measurements of past atmosphere come from bubbles trapped in ice cores

Past temperature recorded in oxygen isotopes; 4-12 deg C variation between ice ages

These records show a correlation between greenhouse gas concentrations and temperature

Greenhouse gases and temperature

Current temperature increase a sharp change from past 1000 years

Climate might otherwise be cooling,but this is speculation

Greenhouse gases

Greenhouse gas sources

Methane Tg/yr

Animals 80Termites 40Rice Paddies 110Wetlands 115Fuels 180

Total 525

Yellow text = anthropogenic source

Nitrous Oxide Tg/yr

Biomass burning 2Land use (agriculture) 1.4Denitrification (soil) 5.7Denitrification (ocean) 2

Total 11.1

Greenhouse gas sources

Yellow text = anthropogenic source

Greenhouse gas sources

Carbon Dioxide Pg/yr

Fossil Fuel 6.3Land clearing 1.7Ecosystem respiration 120Ocean efflux 105

Yellow text = anthropogenic source

The global carbon balance(in Pg C year-1):

From: IPCC 1995

5.5

1 Pg = 1015 grams

Fossil fuels + deforest. = atmosphere + oceans + ???

Eff + Edf = atm + ocean + other

+ 1.8+ 1.6 = 3.3 + 2.0

Predicting climate

Climate predictions

• General circulation models (GCM) are used to predict future climate

• Driven by physical processes that involve transfers of energy and water

• Used with different greenhouse gas ‘scenarios’ to predict climate in a future atmosphere

GCM predictions

• Models are tested against climate records from the past

• Model predictions are compared with other similar GCM predictions

• GCM temperature predictions are typically quite accurate

GCM predictions

• Global climate predicted to warm 1.5 - 6 deg C by 2050 if CO2 increases at current rate.

• High latitudes & and land surfaces warm most.

• Washington DC now has 30 days over 90 deg F. Will have 85 days over 90 deg F.

Gainesville is not predicted to change very much.

Why?

GCM predictions

• GCM precipitation predictions are more variable and considered less accurate

GCM predictions

• Changes in precipitation are more variable globally

• Wet tropics may become wetter

Arid zones may become drier

GCM predictions

Wamer temperatures = more energy

More energy = larger storms

How will climate warming affect life in FL?

Sea level change in FL