• Greenhouse gases in our atmosphere are responsible for making our planet habitable
• Without greenhouse gases in our atmosphere the Earth would be about 60 degrees F cooler
• Increasing greenhouse gas concentrations in the atmosphere will increase the Earth’s equilibrium temperature
• CO2 and methane are some of the “non-condensing” greenhouse gases
• Water vapor is a “condensing” greenhouse gas and it’s atmospheric concentration is primarily correlated to temperature

• The sea levels rose about 30 feet/ oF as the Earth warmed after the last glacial maximum6
• Based on the CO2 emitted to date (the atmosphere is currently at about 400ppm), we should plan for a sea-level rise of at least 45 feet.7
• Temperatures have varied about 1.8 over the last 10,000 years

• Earth’s average temperature has increased about 1.8 degrees F
• Atmospheric concentration of CO2 has increased from about 270ppm to about 400ppm
• The burning of fossil fuels by humans have emitted about ___ gigatons of CO2
• ___ gigatons of CO2 have been added to the atmosphere
• ___ gigatons of CO2 have been added to the oceans

• The Earth currently receives more energy from the sun than it emits
• The oceans absorb about 80% of the “excess” energy
• The Earth (oceans and atmosphere) have been warming at a relatively steady rate for about 40 years
• During the last 15 years more of the “excess” energy has gone into the oceans (and less into the atmosphere), resulting in smaller increase in the Earth’s atmospheric temperature
• Atmospheric concentrations of CO2 are increasing about 2ppm/year
• Much of the atmospheric CO2 originated from burning of fossil fuels
• The volume of Arctic ice has been declining steadily since 1990, and the Arctic is expected to be ice-free in the summer sometime in the next 20-30 years.

• CO2 emissions
• Sea level rise
• How the climate will change

(fast feedbacks are things that happen quickly – years to decades)
• The volume of the oceans will increase due to thermal expansion
• Glaciers will lose mass, increasing the sea level
• The atmosphere will contain more moisture
• For every degree C increase, water vapor increases 6 to 7.5%
• The shifting of the ranges of the plants and animals that require specific temperature ranges

(slow feedbacks are things that happen slowly – decades to centuries to millennia)
• Arctic ice will melt and the newly-ice free waters will absorb energy instead of reflecting it
• The “snow line” will retreat and the newly snow-free land absorb energy instead of reflecting it
• Trees will replace shrubs in the Arctic, and trees absorb more energy than shrubs
• Some of the organic carbon (in permafrost, peat bogs, etc.) will decompose
• Some of the methane from methyl hydrates will be released
• Sea level rise of 20-30 feet for each degree of warming
• The Greenland ice sheet will likely melt

• “Climate sensitivity” is a metric for describing how sensitive the Earth’s temperature is to doubling of atmospheric CO2
• “Transient climate sensitivity” – the change over years to decades – does not include “slow feedbacks”) – estimated to be between 1.5°C and 4.5°C, with a likely value of about 3
• “Earth system climate sensitivity” – the change over decades to centuries to millennia– includes “slow feedbacks”) – may have a value of between 4°C and 6°C
• When trying to predict how much the Earth will warm in the decades and centuries ahead, “climate sensitivity” is the only metric that really matters.

If one looks at the facts and observations of global warming, it is only possible to conclude that the Earth is warming and that humans are primarily responsible. Therefore the only “unknowns” are how much the Earth is likely to warm both in the near term and in the long term and how the climate is likely to change. The “near term” forecast is not promising, particularly since there is not even a hint that global leaders are taking the problem seriously.

http://www.ucar.edu/learn/1_3_1.htm
http://nova.stanford.edu/projects/mod-x/id-green.html
http://www.giss.nasa.gov/research/briefs/lacis_01/
http://www.munfw.org/archive/40th/unep4.htm
http://www.nasa.gov/topics/earth/features/co2-temperature.html
http://ossfoundation.us/projects/environment/global-warming/myths/images/sea-level/Post-Glacial_Sea_Level.png/view
http://www.pnas.org/content/early/2013/01/03/1216073110.abstract
http://www.wsws.org/en/articles/2013/05/13/warm-m13.html