Variable scenarios GLOBAL WARMING Temperatures are rising General principles, not numbers. GLOBAL WARMING “Greenhouse Effect” Solar Energy Balance (complicated mass balance problem) Three notable points about this graph 1 2 3 How does one ‘read’ past temperatures from ice?
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How does one ‘read’ past temperatures from ice?
Isotope formation (C, N,..) is temperature dependent.
Isotopes are in equilibrium in atmosphere.
Deposition captures a signal of the isotope ratio of the atmosphere
This isotope ratio can be calibrated to detect a climate signal.
Deposition can come from ice cores (H2O, CO2), diatoms (calcium carbonate), or other hard sediments.
Variation in the Earth’s orbit causes variation in solar energy absorbed and drive long term climate change
Al Gore “AIT” point: --The 10 warmest years on record have ALL been in the last 14 years.---
The trouble with temp:
1900 1920 1940 1960 1980 2000
Recently, temps are up, up, up
Gases vary in heat trapping abilities. Larger molecules trap more heat. Larger molecules also remain in atmosphere longer.
985 1185 1385 1585 1785 1985
Climate: a collection of the earth’s weather
December, January February June, July, August
Predicted Temperature Increase: greatest at high latitudes during the winter months
Fig. 2. Average snowpack SWE for 2020-2049 and 2070-2099 expressed as a percent of the average for the reference period 1961-1990 for the Sierra Nevada region draining into the Sacramento-San Joaquin river system
Hayhoe, Katharine et al. (2004) Proc. Natl. Acad. Sci. USA 101, 12422-12427
Copyright ©2004 by the National Academy of Sciences
3.5-8.5oC at equilibrium
Think about this as a probability distribution with 3.5 and 8.5 equally likely, but 5.5 much more likely than either.
Dr. R K Pachauri
Intergovernmental Panel on Climate Change
Saturday, 17 November 2007
INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (IPCC)
Different scenarios focus on different human behaviors
Nov. 30, 2005
North Atlantic current slows by 30% relative to 50 years ago.
--Driven by fresh water inputs (rain and ice melt).
--Predicted by warming models.
--Consequence: cooling in Europe.
GCM’s predict mean outcomes, but not frequencies of extreme events, making it tough to say whether recent increase in hurricane frequency and intensity is natural variation or anthropogenic