mar110 lecture #28 climate change – i

25 November 2007 MAR 110 Lec28 Climate Change I

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MAR110 LECTURE #28 Climate Change – I

Figure 28.2 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)

Figure 28.1 Climate Change Diagnostics Drought and flooding represent just a couple of hazards related to climate variability (O)


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Figure 28.3 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 ice-ocean, and air-ocean interaction processes that include heat transfers, precipitation/evaporations, and wind effects. (?)

EARTH SYSTEM EARTH SYSTEM CLIMATE CHANGE FACTORSCLIMATE CHANGE FACTORS

Lots of Components!Lots of Components! ……interact interact on many different on many different Time ScalesTime Scales

RESULT RESULT --> MANY KINDS OF CLIMATE VARIATIONS > MANY KINDS OF CLIMATE VARIATIONS

Figure 28.4 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. (??)


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Temperature

..a Climate ChangePROXY

“…varies on many time

scales”

4 3 2 1 0.57 0.225 0.065 0.002Billion Years Ago

Figure 28.6 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.

Figure 28.5 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)


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Climate Change: Multiple Climate Change: Multiple TimeTime--ScalesScales

Hypothetical ClimateHypothetical Climate HistoryHistory with with Two Time Scales…Two Time Scales…

~35~35 ~40~40 ~40~40

…….an Upward Trend + 35.an Upward Trend + 35--40 Year Cycle40 Year Cycle

Figure 28.7 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)

Figure 28.8 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)


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Climate Change Time Scale :Climate Change Time Scale : ENSO ENSO 3 3 -- 7yr7yr

Figure 28.10 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)

Climate Change Time Scale: AnnualClimate Change Time Scale: Annual

Figure 28.9 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)


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Climate Change Time Scales : Climate Change Time Scales : 1000yr Ocean Conveyer Belt1000yr Ocean Conveyer Belt

TWOTWOMODES!MODES!

Figure 28.12 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)

Climate Change Time Scale: AnnualClimate Change Time Scale: Annual

Figure 28.11 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)


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SEASONALSEASONALMONSOON MONSOON

VARIABILITYVARIABILITY

Figure 28.14 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.

Figure 28.13 Conveyor Belt ON!


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Estimated Global Temperature & PrecipitationEstimated Global Temperature & Precipitation

Earth has been generally COOLING BUT

it is a “quivering” decline!

..for the past 55 MY

Figure 28.16 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)

Figure 28.15 Conveyor Belt OFF!


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Recording Climate Change Recording Climate Change including volcanismincluding volcanism

Figure 28.18 Recording Climate Change The annual layers of ice that are laid down in Greenland and Antarctica preserve physical and chemical evidence regarding climate. (SA)

Abrupt Climate Change Abrupt Climate Change -- Scientific American Nov 2004 Scientific American Nov 2004

Lots of Lots of SupportingSupportingEvidence !Evidence !

Figure 28.17 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)


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Ice Volume Change : 10,000 Year Time-Scales

Abrupt Climate Changes

Interglacial PresentInter-glacial

Most RecentGlacier

Figure 28.20 Ice Volume Change This record of estimated ice volume shows that there was less ice volume during the interglacial period 130 kya than there is during the present interglacial (i.e. present). However the ice core record indicates that the transition has not been smooth with many episodes punctuated by abrupt climate change. (XX)

Ice Core Climate HistoriesIce Core Climate Histories

Figure 28.19 Climate Change Histories There is mounting evidence from ice cores extracted from Antarctica and Greenland that significant abrupt climate changes has occurred (SA)


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Possible Consequence of Abrupt Climate ChangePossible Consequence of Abrupt Climate Change

Figure 28.21 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)

Climate Change Time Scales: Climate Change Time Scales: 1010-- 100ky100ky Orbital ChangesOrbital Changes

Figure 28.22 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)


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Climate Change Time Scales : Climate Change Time Scales : 1010--100my100my Plate TectonicsPlate Tectonics

Figure 28.23 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).

mar110 lecture #28 climate change – i

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