ATMO 336 1st Edition Lecture 28Outline of Last Lecture II. Were climates of earth always as they were today?III. Why do we need to understand the climates of the pastIV. How do we know what climate was like in the pasta. Proxy recordsb. Environmental indicatorsV. Before the PleistoceneVI. The Pleistocenea. The pastb. Connection to present day climatec. Important points from the PleistoceneVII. Slight variations in the earths orbital parametes have resulted in significant climate changea. Paleoclimate perspectiveb. Cycles in earths orbital parametersi. Eccentricityii. Obliquityiii. PrecessionI. Milutin milankovich and his discoverysOutline of Current Lecture VIII. Observed temp changes since 1850IX. Implications of temp changes since 1850X. Global warming discussionCurrent Lecture- Observed temp changes since 1850o At most observing locations, the instrumentation is changed over time and adjustmnets must be made to account for differences in how different thermometers measure temp. Urbanization (city building) happened around measuring site Urban areas warmer than rural areas due to building materials and their ability to retain heat better and heat generated within cities = urban heat island effecto Adjustments must be made to properly represent the global average from observing networkThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Where there is sparse coverage of observations, it is more difficult to determine the true average temperature over a large region from just a few observationso Estimates indicate that the surface temp has risen at least .5 degreees C since 1850 (most agree that the global average has increased)o Even if global average goes up, there will be quite a bit of variability at regional spatial scales= thus, it would be incorrect to ague that global warming is not happening becausethere are small regions that show cooling- Implications of temp changes since 1850o Warming large due to the additional greenhouse gaseso Irregular warming since 1850 use by opponents of anthropogenic warming as evidence that natural climate fluctuations dominate over the effects caused by greenhouse gases. Points to two periods: Large warming that occurred from 1910-1940 (warming too rapid and hard to explain with little greenhouse gas inputs= natural change in global average temp) Cooling trend from 1940-1970 (cooling even though greenhouse gas concentrations were increasing= natural fluctuations were larger influence than greenhouse gases)o Warming from 1980-2002 more consistent with theory that says recent temps changes are large the result of increasing greenhouse gases (this does NOT prove cause and effect, and this is not proof that increasing greenhouse gases have been responsible for most of the warmingo Through year of 2014, 19 of the previous 20 years rank among the 19 warmest years in measured record which began ni 1860. However, medieval period global average temp may have been close or slightly warmer than todayo Global average temp has not increased since at least 2002 Pause (or hitaus) in global warming= does not validate conecction between higher greenhouse gases and higher global average temperature- Global warming discussiono Although we are able to measure a significant rise in global average temps, we are unable to determine how much of the warming is due to the increases in greenhouse gasses and know much is apart of the natural cycleo We are unable to predict exactly how climate will change in the future with higher levels of greenhouse gases and what impacts this would meano Concentration of CO2 is greater now than any time over the last several hundred thousand yearso Researchers are predicting that there will be global cooling based that we are beginning a period of lower solar activity and/or a cold phase of the PDO.o Possibility that future climate changes due to anthropogenic greenhouse gas emissions will be even more sever than the predictions of current climate models Large, regional climate shifts may occur (gulf stream ocean circulation shuts down) Are there strong positive feedback systems that have yet to kick in? Is there a threshold in either temp or greenhouse gas concentrations that once we pass, the climate system will shift abruptyly to another stateo Ocean acidificaiton (CO2 issue) which may affect life cycles of marine