Climate Drivers: Internal Global Change Ecology PBIO 275

External Drivers -Sunspot Cycles -Orbital Variations Internal Drivers -Plate Tectonics -Volcanic Activity -Albedo -Greenhouse Effect External and Internal Drivers of Climate

Climate Drivers Distribution of heat

Incoming radiation Outgoing IR radiation

Latitudinal differences in net energy balance cause atmosphere and ocean circulation

Denser waters in high latitude oceans create a thermohaline circulation system that has a major impact on regional climates

Questions: How can warming climate shut down thermohaline circulation? How would this influence climate?

Wisconsin glaciation of North America Holocene Pleistocene A general picture of climate change over the last 18,000 years

Figure SPM.6

Climate Drivers Plate Tectonics

Pangaea 300 million years ago Today

Plate Tectonics over the last 700 million years

25-35 million years ago Impacts: Ocean Circulation

Impacts: CO 2 Cycle

Plate Tectonics 1.Influences latitudinal transfer of heat by ocean and atmosphere. 2.Allows accumulation of ice sheets near the poles. 3.Exerts long term control on CO 2 levels through volcanic activity, weathering, and burial of organic carbon.

Questions: How do you think the rate of movement of continental plates influences climate? What would the effect of an increased rate of movement be on climate? Is this relevant to current climate change?

Climate Drivers Albedo or Reflectance

Albedo The amount of solar radiation reflected or scattered back into space without any change in wavelength. The mean global albedo is about 30%. The albedo of different land surfaces varies greatly from 90% to less than 5%.

SurfaceAlbedo Tropical Forest Woodland (deciduous) Woodland (coniferous) Grassland Sandy desert Tundra Sea water0.10 Water (0-60º)<0.08 Water (60-90º) Fresh Snow Sea ice Clouds (low) Clouds (high)

Questions: What is the effect of melting sea ice on albedo and climate change? What is the effect of deforestation on albedo? Is is it a negative feedback? What is the effect of desertification on albedo? Will it slow warming at least regionally?

Albedo effects if earth were completely forested, desert, water, or ice.

Land use and albedo effect on radiative forcing

Past Change

J. J. Feddema et al., Science 310, (2005) Fig. 1. Representation of present-day land cover and land-cover change for each of the scenarios

J. J. Feddema et al., Science 310, (2005) Fig. 2. JJA and DJF temperature differences due to land-cover change in each of the scenarios

Climate Drivers Aerosols

Aerosols are small airborne particles and droplets. Direct effect: Affects incoming and outgoing radiation Indirect effect: Affects cloud formation (condensation nuclei) Some sources: sulfates, organic carbon, black carbon (fossil fuels) Short-lived in the atmosphere (< 1 year) Overall effects are not well understood, dependent on particle size, and direct and indirect effects.

Figure 2.10

Figure 7.20

Volcanic Activity Mt. St. Helens, May 1980

Volcanic Ash Downwind of Mt. St. Helens

Eruption of Mt. Pinatubo, Philippine Islands, April 1991

Timeline of Troposphere temperature Timeline of lower stratosphere temperature

Tambora (Indonesia), eruption 1815: 150 km 3 of ejecta 90,000 dead (26 of 12,000 on island survived) For comparison: Krakatoa (Indonesia), eruption 1883: 20 km 3 of ejecta Mt. St. Helens, eruption 1980: <1 km 3 of ejecta Other eruptions in same period: 1812: Soufriére (St. Vincent) 1814: Mayon (Phillippines)

1816: The year without a summer Danville (VT) North Star (15 June 1816) Melancholy Weather "Some account was given in last week's issue of the unparalleled severity of the weather. It continued without any essential amelioration, from the 6th to the 10th instant--freezing as hard five nights in succession as it usually does in December. On the night of the 6th, water froze an inch thick -- and on the night of the 7th and morning of the 8th, a kind of sleet or exceeding cold snow fell, attended with high wind, which measured in places where it was drifted, 18 to 20 inches in depth. Saturday morning the weather was more severe than it generally is during the storms of winter. It was indeed a gloomy and tedious period."

“Eighteen Hundred and Froze to Death” (1816) At least one frost each month of the summer: May 12: Frosts penetrate to Pennsylvania and Virginia May 30: Frosts penetrate to Rhode Island Erie Pennsylvania had 1/4 inch ice Emerging corn killed in Maine June 5-9: Winter storm in VT and upstate NY. Frosts reach central MA July 6: Frost in northern New England. Kills crops in NH. 40° in MA August 13: Frost in northern New England August 20: Severe cold front with frost following, kills corn in southern NH Mid September: Frosts in Northern New England September 27: Major frost ends dismal growing season. Source:

Indicators of the Human Influence on Sulphate aerosols during the Industrial Era Source: IPCC TAR 2001

Figure 7.24

Radiative forcing (W/m2) Solar and volcanic forces have affected the climate system

Figure SPM.2

Putting this all together… Tectonics, albedo, and volcanoes.

Volcanoes and CO 2

Earth Homeostasis

Questions: 1.How is the earth’s climate system maintained in a long-term equilibrium? 2.How do we expect the earth’s ‘thermostat’ to respond to current anthropogenic greenhouse gas forcing? 3.Can you imagine a scenario where we push the system outside of its ability to respond? 4.How might we use our understanding of this homoestasis mechanism to help with current anthropogenic forcing?

Snowball Earth The trigger: ice forming at latitudes as low as of 30° The escape: CO 2 levels 350x higher than today -635 million years ago -Lasting ~12 million years -Oceans froze to depth of 1km

Climate forcing mechanisms MechanismTime period 1. Solar Forcing Solar intensity (sunspots)(10’s to 100’s of years) Orbital Variations(Thousands of years) 2. Plate Tectonics (Millions of years) Mountain building, continent locations 3. Albedo(all time scales) 4. Aerosols(1-10 years) Volcanoes, pollution 5. Greenhouse Effect (all time scales) CO2, Methane, Water vapor 6. Land use( 1 to 100’s of years )

Radiative Forcing of Climate Change Radiative forcing is the global average impact on surface or troposphere temperature due to natural or human- caused (anthropogenic) causes. Forcing agents (or mechanisms) that cause climate change Greenhouse gases CO 2 (Carbon dioxide) CH 4 (Methane) N 2 O (Nitrous oxide) Halocarbons Aerosols Ozone Land-use effect on albedo Solar How much do we know about how these agents change the climate? How have these agents changed over time?

Sunspot Cycles (Decades) Orbital Variations (Thousands of years) Plate Tectonics (Millions of years) Volcanic Activity (1-3 years) Albedo (All time scales) Greenhouse Effect (All time scales) Drivers of Climate Change (forcing mechanisms)