1. BEFORE reading the information on uncertainty in the IPCC AR5 Report, what is your understanding about how certain scientists are regarding climate change? Make sure you provide a number representing the level of certainty.
2. Read each of the following statements that can be found in the Summary for Policymakers of the Fifth Assessment Report by the IPCC on the state of our understanding of Climate Science and describe how confident the scientists are with each statement (list the probability that the statement is true).
a. It is virtually certain that globally the troposphere has warmed since the mid-20th century.
b. Changes in many extreme weather and climate events have been observed since about 1950. It is very likely that the number of cold days and nights has decreased and the number of warm days and nights has increased on the global scale.
c. It is likely that the frequency of heat waves has increased in large parts of Europe, Asia and Australia.
d. The annual mean Arctic sea ice extent decreased over the period 1979 to 2012 with a rate that was very likely in the range 3.5 to 4.1% per decade, and very likely in the range 9.4 to 13.6% per decade for the summer sea ice minimum (perennial sea ice).
e. The average rate of ice loss from the Greenland ice sheet has very likelysubstantially increased from 34 Gt/yr over the period 1992 to 2001 to 215 Gt/yr over the period 2002 to 2011.
f. It is very likely that the mean rate of global averaged sea level rise was 1.7 mm/yr between 1901 and 2010, 2.0 mm/yr between 1971 and 2010, and 3.2 mm/yr between 1993 and 2010.
g. Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes. This evidence for human influence has grown since AR4. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.
h. Greenhouse gases contributed a global mean surface warming likely to be in the range of 0.5°C to 1.3°C over the period 1951 to 2010, with the contributions from other anthropogenic forcings, including the cooling effect of aerosols, likely to be in the range of −0.6°C to 0.1°C. The contribution from natural forcings is likelyto be in the range of −0.1°C to 0.1°C, and from natural internal variability is likely to be in the range of −0.1°C to 0.1°C. Together these assessed contributions are consistent with the observed warming of approximately 0.6°C to 0.7°C over this period.
i. Global surface temperature change for the end of the 21st century is likely to exceed 1.5°C relative to 1850 to 1900 for all RCP scenarios except RCP2.6. It is likelyto exceed 2°C for RCP6.0 and RCP8.5, and more likely than not to exceed 2°C for RCP4.5. Warming will continue beyond 2100 under all RCP scenarios except RCP2.6. Warming will continue to exhibit interannual-to-decadal variability and will not be regionally uniform.
j. Based on your answers to Part i, how much do you think the global surface temperature will increase (relative to the 1850-1900 average) by 2100?
k. Now that you have read the article on Uncertainty in the Sciences and the report on how the IPCC treated uncertainty in the IPCC 5th Assessment Report, what is your understanding about how certain scientists are regarding climate change? Make sure you provide a number representing the level of certainty
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