The Basic Science of Climate Change

Janina MorettiSeptember 6, 2012

Overview

• Basic science of climate change:– What is climate change? What is causing it?

• Global and local impacts of climate change• Climate change tipping points • Climate change solutions

Number of scientific studies dealing with “climate change” published in scientific journals between 1993 and 2003: 928

0Number disagreeing with the global consensus that greenhouse gas pollution has caused most of the warming of the last 50 years:

Science, December 3, 2004 Vol. 306, Issue 5702,1686

There is a scientific consensus: greenhouse gas emissions are causing climate change

The greenhouse effect

http://www.ecy.wa.gov/climatechange/whatis.htm

In the past 100 years we have been burning a lot of fossil fuels. . .

CO2

CO2

CO2

CO2

CO2

CO2

CO2 +0.8°C (1.4°F)

CO2

CO2

CO2

CO2

CO2

CO2

CO2 +0.8°C (1.4°F)

Burning fossil fuels increases the concentration of carbon dioxide in the atmosphere

More carbon dioxide in the atmosphere warms the planet

CO2

CO2

CO2

CO2

CO2

CO2

CO2 +0.8°C (1.4°F)

What is 350ppm? 550ppm??!

275ppm

Now: 392ppm

We are already experiencing climate change impacts

• Temperature rise• Sea level rise• Loss of glaciers• More frequent extreme weather events

(droughts, floods, hurricanes, wildfires)• Ocean acidification

Temperature is rising

http://www.nasa.gov/home/hqnews/2012/jan/HQ_12-020_2011_Global_Temp.html

• 9 of the 10 warmest years in the modern meteorological record have occurred since the year 2000

• July was the hottest on record for the United States (27,000 high temperature records were broken or tied.)

The Arctic is currently warming at twice the rate of the rest of the world

1979 2007

Between 1979 and 2007, the Arctic lost over 40% of its ice

The Arctic is currently warming at twice the rate of the rest of the world

More frequent droughts

This summer over half the United States is in extreme or moderate drought. Decreased crop yields have caused a 10% spike in food prices.

Climate change impacts San Diego County

More intense and frequent wildfires

Water Shortages

Beach erosion and coastal floodinghttp://www.sdfoundation.org/

We need to act fast to avoid triggering feedback loops

We need to act fast to avoid triggering feedback loops

More examples:• Desertification of the Amazon rainforest• Melting of the Greenland ice sheet• Melting of the West Antarctic ice sheet• Methane release from permafrost melt• Monsoon shift in India

How do to avoid tipping points?

The Three Simple Numbers

1) 2°C (3.6°F)

2) 565 GT CO2

565 GT CO23) 2,795 GT CO2

2,795 GT CO2

Can we stabilize at 2°C?Business as Usual: 95% reduction by 2020:

http://climateinteractive.org/simulations/climate-momentum-simulation/climate-momentum

Global major contributors to climate change

World Resources Institute, http://earthtrends.wri.org/images/GHG_emissions_by_sector2.jpg

Local major contributors to climate change

http://www.fypower.org/pdf/SanDiegoCounty_GHGinventory.pdf

In San Diego County, on-road transportationand electricity are thelargest contributors togreenhouse gas emissions.

• There are many well-understood solutions

Solutions

Replace fossil fuels with clean

renewable sources

as well as individual actions as consumers• Solutions require both collective action as citizens…

Increase gas mileage for

cars

Conserve electricity,

water & gasIncrease energy efficiency of

existing and new buildings

Change land use & transportation to reduce miles

traveled

Consume less and

waste less

Stop deforestation

Move diets lower on the food chain

Carbon tax & dividend

• Inventory, identify potential solutions, create & implement plan

Climate Facts• There is a scientific consensus that the earth is warming due to human caused

greenhouse gas emissions. • The current atmospheric concentration of carbon dioxide is 392ppm. Before the

industrial revolution is was 275ppm. 350ppm is a safe upper limit.• The impacts of climate change are happening now and faster than previously

though.• Nine of the 10 warmest years in the modern meteorological record have

occurred since the year 2000.• 2°C of global warming is a safe upper limit. We can only emit 565 gigatons CO2

to stay below this limit. Fossil fuel industries have 2,795 gigatons CO2 in reserve.• In San Diego county, the largest contributors to greenhouse gas emissions are

transportation (46%) and electricity (25%).• In San Diego county, the impacts of climate change are rising temperatures,

water shortage, sea level rise, and more frequent and intense wild fires.• There are known solutions to climate change, but we need to implement them

quickly, on a large scale.

Useful References• Climate Progress: http://thinkprogress.org/climate/issue/The latest news on climate change science, solutions, and politics

• Skeptical Science: http://www.skepticalscience.com/Climate science summarized for a general audience. Includes an

extensive list of climate myths debunked.

• Just the Facts-CA: http://www.opr.ca.gov/s_climatechangefacts.phpBasic facts and science of climate change