Global warming Summary evidence

Transcription

1 Global warming Summary evidence

2 Learning goals Observations of global temperature change How/why we can be confident in the results Difference between forcing and response Notion of an interaction The concept of feedbacks Be able to recognize positive and negative feedback loops

3 (Full report to be released 30 January 2014) Observed global mean combined land and ocean surface temperature anomalies, from 1850 to 2012 from three data sets. Top panel: annual mean values. Bottom panel: decadal mean values including the estimate of uncertainty for one dataset (black). Anomalies are relative to the mean of IPCC, 2013: Summary for Policymakers. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, in press

4 Could this be wrong!? Try googling: global temperature warming false. Apparently some people have strong opinions. What about the facts?

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6 Same result from multiple datasets Proxy temperature records are independent of thermometers

7 Clickers questions Test question: The most awesome class so far this semester is: A. ATOC 1060

8 Is warming the same everywhere? A. Warming is the same everywhere B. Warming is largest near the equator C. Warming is largest over land D. Warming is largest over the ocean E. Warming is largest in Antarctica

9 Map of the observed surface temperature change from 1901 to 2012 derived from temperature trends determined by linear regression from one dataset (orange line in panel a). Trends have been calculated where data availability permits a robust estimate (i.e., only for grid boxes with greater than 70% complete records and more than 20% data availability in the first and last 10% of the time period). Other areas are white. Grid boxes where the trend is significant at the 10% level are indicated by a + sign.

10 Is warming the same everywhere? A. Warming is the same everywhere B. Warming is largest near the equator C. Warming is largest over land D. Warming is largest over the ocean E. Warming is largest in Antarctica

11 Maps of observed precipitation change from 1901 to 2010 and from 1951 to 2010 (trends in annual accumulation calculated using the same criteria as in Figure SPM.1) from one data set.

12 Precipitation changes... A. Are more well known than temperature changes B. Are known to be larger over land C. Are generally increasing in the eastern US D. Are definitely decreasing in Colorado E. Are irrelevant for climate change

13 Now measured by NOAA-Global Monitoring Division in Boulder and INSTAAR at CU Over 400 ppm last year. Charles (Dave) Keeling Me at Mauna Loa with Keeling's instrument.

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15 Multiple observed indicators of a changing global carbon cycle: (a) atmospheric concentrations of carbon dioxide (CO2) from Mauna Loa (19 32 N, W red) and South Pole (89 59 S, W black) since 1958; (b) partial pressure of dissolved CO2 at the ocean surface (blue curves) and in situ ph (green curves), a measure of the acidity of ocean water. Measurements are from three stations from the Atlantic (29 10 N, W dark blue/dark green; N, W blue/green) and the Pacific Oceans (22 45 N, W light blue/light green).

16 Drilling ice cores Chemical composition of ice related to temperature Also, air bubbles trap CO 2 Ice core samples analyzed at CU-INSTAAR, cores stored at the National Ice-core Lab. in Denver recent 100,000 years 0.5 million years old

17 Data from ice cores Temperature Article by Gavin Schmidt: realclimate.org Figure by T. Stocker.

18 Other indicators of global warming (a) Extent of Northern Hemisphere March-April (spring) average snow cover; (b) extent of Arctic July-August-September (summer) average sea ice; (c) change in global mean upper ocean (0 700 m) heat content aligned to , and relative to the mean of all datasets for 1970; (d) global mean sea level relative to the mean of the longest running dataset, and with all datasets aligned to have the same value in 1993, the first year of satellite altimetry data.

19 Reading Chapter 2: The Greenhouse effect Rough Guide pages: (also catch up on 1-22 if not read yet) Next week: Homework assignment 1

20 Help! David Noone: office hours: Tuesday 2-5pm Ariel Morrison (TA): office hours TBD LAs: Drop in study sessions (Monday 2-3, Tuesday 11-12:, Thursday 10-11, 11-12, 6-7pm) Genziana Pando Kelly Gjestvang Mark.Leonard Excellent for homework and formulating discussion questions.