What climate change means

Climate consists of averages & extremes of– hot & cold

– wet & dry

– snowpack & snowmelt

– winds & storm tracks

– ocean currents & upwellings

Small changes in global-average surface Temperatures may cause consequential changes in climate patterns.

?? Climate Change or

Global Warming ??

DifferenceGLOBAL WARMING

is the increase of the Earth’s average surface temperature due to a build-up of greenhouse gases in the atmosphere.

CLIMATE CHANGE is a broader term that

refers to long-term changes in climate, including average temperature and precipitation.

The stakes in climate change

Climate governs, so climate change alters,

• productivity of farms, forests, & fisheries

• prevalence of oppressive heat &humidity

• geography of disease

• damages from storms, floods, droughts, wildfires

• property losses from sea-level rise

• expenditures on engineered environments

• distribution & abundance of species

What Evidence is cited?

• Temperature records in the atmosphere and the oceans, and from ice cores, bore holes, tree rings, corals, pollens, sediments, and more – the Earth’s climate is changing …….

• at a pace outside therange of expected natural variation

• in the opposite direction from what the natural cycle would be

What Evidence is cited?

• Predictions show the Earth should be cooling, but we are warming up:

• ~0.8 C in the last 125 years

What Evidence is cited?

• The 12 warmest years of the last 125 have all occurred since 1990

• 20 of the 21 warmest have been since 1980.

• The last 50 years appear to have been the warmest half century in 6000 years.

Further Evidence of a changing climate……

Further evidence of a changing climate

As expected in a warming world, observations overrecent decades also show…

• Evaporation & rainfall are increasing;

• Coastal glaciers are retreating;

• Mountain glaciers are disappearing;

• Permafrost is thawing;

• Sea ice is shrinking;

• Greenland is melting;

• Sea level is rising;

• Species are moving.

Evaporation & precipitation are increasing

NCDC, 2000

Effect is not uniform; most places getting wetter, some getting drier.

Muir Glacier, Alaska, 1941-2004

NSIDC/WDC for Glaciology, Boulder, compiler. 2002, updated 2006. Online glacier photograph database. Boulder, CO: National Snow and Ice Data Center.

August 1941 August 2004

Coastal glaciers are retreating

Mountain glaciers are disappearing

Permafrost melts when T ≥ 0°C ACIA 2004

Permafrost is thawingAverage annual ground temperature, Fairbanks, AK

°C

                           

NASA photograph

Extent of Arctic summer ice in 1979 and in 2003.

N. Polar ice cap is floating so it does not change sea level when it melts.

But the reduced reflectivity when the ice is replaced by water amplifies the warming effect.

Sea ice is shrinking

NATURAL INFLUENCES ON THE GLOBAL CLIMATE

• EXAMPLES…….– variations in the energy output of the Sun

– variations in the Earth’s orbit and tilt

– changes in the composition of the atmospheric from volcanoes, biological activity, weathering of rocks

• EXAMPLES…….– rising concentration of “greenhouse gases” from

deforestation, agriculture and fossil-fuel burning

– rising concentration of particulate matter from agricultural burning and fossil-fuel burning,

– alteration of the reflectivity of the Earth’s surface by deforestation, desertification

– increased high cloudiness from aircraft contrails

HUMAN INFLUENCES ON THE GLOBAL CLIMATE

Fossil fuels (coal, oil, natural gas)

Carbon Dioxide (CO2)

Greenhouse GassesGreenhouse gasses absorb some of the heat and trap it near the earth's surface, so that the earth is warmed up. This process, commonly known as the greenhouse effect.

The Sun’s energy passes through the car’s windshield.

This energy (heat) is trapped inside the car and cannot pass back through the windshield, causing the inside of the car to warm up.

How Does that

WORK?

Video: http://youtu.be/Hi3ERes0h84

• The amount of heat depends on concentrations of atmospheric greenhouse gasses and the amount of time these gasses stay in the atmosphere.

• The most important are – carbon dioxide (CO2)

– CFC's (Chlor-Fluoro-Carbons), – nitrogen oxides– methane.

One Cause the greenhouse effect

Global Atmospheric Concentration of CO2

The choicesFacing these, we have 3 options:

• Mitigation: Take measures to reduce the pace and severity of the changes

• Adaptation: Take measures to reduce the negative effects on human well-being resulting from the changes that do occur.

• Suffering: Accept the adverse impacts that are not avoided by either mitigation or adaptation.