MAR 110: Lecture 22 Outline Climate Change 1 MAR110 LECTURE #22 Climate Change Climate Change Diagnostics Drought and flooding represent just a couple of hazards related to climate variability (O) The Atmosphere/Ocean/Earth Climate System A schematic of the atmosphere/ocean/earth climate system - indicating the important roles of the (1) incoming solar radiation, (2) atmosphere, (3) oceans, (4) water cycle, (5) clouds, (6) ice, (7) land, and (8) human influences in a complex mixture of processes. The air-ocean interaction processes include heat transfers, precipitation/evaporations, and wind effects. Air-ice and ice-ocean couplings are implied. The role of water vapor in blocking outgoing infrared radiation in connection with the greenhouse effect is indicated in the inset. (SA)
MAR 110: Lecture 22 Outline Climate Change 2 Climate Variability of the Atmosphere/Ocean/Earth System This schematic indicates the important roles of changes in incoming solar radiation, greenhouse gases, clouds, land & vegetation, ocean basin shape, and ocean properties in a climate systems. Overall climate change is a complex mixture of processes that are mediated by air-ice and iceocean, and air-ocean interaction processes that include heat transfers, precipitation/evaporations, and wind effects. (?) Climate System Schematic The mechanics of climate change are very complex with many feedback loops and variables that make it difficult to predict or to determine which even is the cause and which is the effect between two particular elements of the system. (??)
MAR 110: Lecture 22 Outline Climate Change 3 Estimated Temperature Variability Over Past 4.6 Billion Years The time scales associated with this record of estimated global temperatures from the past 4.6 billion years range from billions of years to a few 10s of thousands of years and are overlapping. Note that present-day temperatures are colder than much of history and pre-history. ( XX) Multiple Climate Change Windows Slices of the (below) 4.6 billion year estimated temperature show (above-1) the basic temperature decrease over the past 65 million years since the asteroid impact wiped out the dinosaurs, (above-2) the modest temperature increase 10kya after the Ice Age (peaked 20kya) followed by a wavering decrease into the Little Ice Age 500yra, before (above-3) the warming trend of the past 100 years or so.
MAR 110: Lecture 22 Outline Climate Change 4 Model Climate Variation With Two Time Scales This hypothetical temperature climate history illustrates the a 35-40year cycle superimposed record-long (~150 years) upward trend that itself could be (we do not know) part of a cycle with a 1000 year cycle. (XX) Recent Global Warming Reconstructed global temperature and carbon dioxide records from the past 100 years. The question is.. Is the recent temperature increase human-induced (anthropogenic) or part of a longer term natural cycle? (SA)
MAR 110: Lecture 22 Outline Climate Change 5 Sea level increase relative to fossil fuel consumption (from Robinson et al. 2007). Seasonal Changes Seasonal changes are part of the natural climate cycle that is linked directly to the revolution of the Earth around the sun. Because the Earth s spin axis tilted, the northern hemisphere to intercepts more sunlight in spring-summer (between 21 March and 21 September equinoxes) it is warmer than during the other half of the year. (XX)
MAR 110: Lecture 22 Outline Climate Change 6 ENSO Changes During normal times the tropical trade winds force a large warm pool of ocean water toward the western tropical Pacific. However the trade winds are part of a basin-scale atmospheric circulation called the Walker Circulation, which oscillates because of air-sea interaction. During the El Nino phase of the oscillation, the trade winds weaken and the warm pool moves eastward flooding the eastern side of the tropical Pacific. The process known as El Nino-Southern Oscillation (ENSO) has an oscillation period that varies between 3 and 7 years. (XX) Solar Intensity Changes Incoming solar radiation varies in intensity as sunspots on the sun s surface appear and disappear (due to internal solar dynamics) on a fairly predictable 22-year cycle. The amplitude of this 22-year variability changes over 100-year time scales, having a subtle effect on climate. (XX)
MAR 110: Lecture 22 Outline Climate Change 7 Thermohaline Circulation Changes The intensity thermohaline conveyor belt circulation, which transports heat from the tropics to the polar regions, can vary on time scales ranging from 100 to 1000 years and affect climate accordingly. (XX)
MAR 110: Lecture 22 Outline Climate Change 8 Conveyor Belt ON! Monsoon Variability The large-scale monsoon winds are driven by the temperature difference between the land and the ocean which changes with the seasons. In summer, when the land is relatively warm, the winds are onshore (see above scematic). In the winter, when the land is cold relative to the ocean, the winds are offshore. The monsoon intensity is sensitive to the size of the temperature difference which is sensitive to climate change.
MAR 110: Lecture 22 Outline Climate Change 9 Conveyor Belt OFF! A Cooling Earth: 65 mya Present Global temperatures have been generally decreasing since the Age of the Dinosaurs ended following what mounting evidence of an asteroid impact in the Gulf of Mexico 65 mya. The temperature decline has been interrupted with abrupt temperature increases and subsequent decreases a quivering decline! (XX)
MAR 110: Lecture 22 Outline Climate Change 10 Abrupt Climate Change There is mounting evidence from ice cores extracted from Antarctica and Greenland that significant climate changes have occurred on time scales from 10 to 100 years (instantaneous on geologic time scales). (SA) Recording Climate Change The annual layers of ice that are laid down in Greenland and Antarctica preserve physical and chemical evidence regarding climate. (SA)
MAR 110: Lecture 22 Outline Climate Change 11 Climate Change Histories There is mounting evidence from ice cores extracted from Antarctica and Greenland that significant abrupt climate changes has occurred (SA) Abrupt Climate Change Consequences The Viking and Mayan civilizations may have been disrupted and even destroyed by abrupt climate change to which they could not adapt. (XX)
MAR 110: Lecture 22 Outline Climate Change 12 Orbital Changes The distance between the earth and the Sun cycles on these very long time scales. Contributions to this distance change include the 1) 20,000-yr precession of the Earth s axis, (2) 40,000-yr wobble of the angle of Earth s tilt axis, and (3) the 100,00-yr variation in the eccentricity in the Earth s orbit around the sun. (XX)
MAR 110: Lecture 22 Outline Climate Change 13 Plate Tectonic Changes The global configuration of the continents changes on the 10 to 100 million time scales of ocean basin formation/destruction. The relative ocean/land configurations have a strong influence on the global climate. (XX).