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 InternalDrivers 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

HolocenePleistocene

A general picture of climate change over the last 18,000 years

Figure SPM.6

Climate Drivers

Plate Tectonics

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: CO2 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 CO2 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%.

Surface Albedo

Tropical Forest 0.10-0.15

Woodland (deciduous) 0.15-0.20

Woodland (coniferous) 0.05-0.15

Grassland 0.16-0.26

Sandy desert 0.30-0.45

Tundra 0.18-0.25

Sea water 0.10

Water (0-60º) <0.08

Water (60-90º) 0.10-1.0

Fresh Snow 0.80-0.95

Sea ice 0.25-0.60

Clouds (low) 0.60-0.70

Clouds (high) 0.18-0.24

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, 1674 -1678 (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, 1674 -1678 (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 Volcanic Ash Downwind of Mt. St. Helensof 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 km3 of ejecta90,000 dead (26 of 12,000 on island survived)

For comparison: Krakatoa (Indonesia), eruption 1883: 20 km3 of ejectaMt. St. Helens, eruption 1980: <1 km3 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 VirginiaMay 30: Frosts penetrate to Rhode Island

Erie Pennsylvania had 1/4 inch iceEmerging corn killed in Maine

June 5-9: Winter storm in VT and upstate NY. Frosts reach central MAJuly 6: Frost in northern New England. Kills crops in NH. 40° in MAAugust 13: Frost in northern New EnglandAugust 20: Severe cold front with frost following, kills corn in southern NHMid September: Frosts in Northern New EnglandSeptember 27: Major frost ends dismal growing season.

Source: http://www.islandnet.com/~see/weather/history/1816.htm

Indicators of the Human InfluenceIndicators of the Human Influenceon Sulphate aerosols during the Industrial Eraon Sulphate aerosols during the Industrial Era

Source: IPCC TAR 2001

Figure 7.24

1900 1950 2000

0

1

-1

-2

-3

-4

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 CO2

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?

SnowballEarth

The trigger: ice forming at latitudes as low as of 30°

The escape: CO2 levels 350x higher than today

-635 million years ago-Lasting ~12 million years-Oceans froze to depth of 1km

Climate forcing mechanisms

Mechanism Time 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

CO2 (Carbon dioxide)CH4 (Methane)N2O (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)