NATS 101 Lecture 25 Climate Change (cont’d)

NATS 101

Lecture 25

Climate Change (cont’d)

Water Vapor

CarbonDioxideOzone

Methane,Nitrous Oxide

WaterWaterVaporVapor60%60%

CarbonCarbonDioxideDioxide26%26%

OO33

8%8%

CHCH44

NN2200 6%6%

Clouds also have a greenhouse effect Kiehl and Trenberth 1997

The Natural Greenhouse Effect: clear sky

CO2 makes the biggest contribution to the climate forcing

Global Warming Potential (GWP)

Different gases has different warming potentials which are defined relative to the warming effect of CO2

Ahrens, Fig 2.10

Gas GWPCarbon dioxide (CO2) 1Methane (CH4) 21Nitrous oxide (N2O) 310Hydrofluorocarbons 560-12,100Perfluorocarbons 6,000-9,200Sulfur hexafluoride 23,900

Changing CO2 concentrations• CO2 concentrations have varied naturally by ~30-50%

over the past few hundred thousand years (ice ages)• Fossil fuel burning since the industrial revolution has

created a recent sharp increase in CO2 concentrations• CO2 concentrations are now higher than at any time in

past few hundred thousand years • And concentrations are increasing faster with time

Last 4 Ice Age cycles:400,000 years

See http://epa.gov/climatechange/science/recentac.html

Man made

You are here

CO2

Temp.

Increasing CO2 concentrations• How high will they go? How warm will it get???• If CO2 concentrations stay within factor of 2 of pre-industrial,

then warming of 3+1oC is expected• If concentrations go still higher => larger uncertainty

because the climate is moving into unprecedented territory

Last 4 Ice Age cycles:400,000 years Man made

You are here

Ice age CO2 range

You are going to be somewhere in here

See http://epa.gov/climatechange/science/futureac.html

Multi-model global averages of surface warming (relative to 1980-99) for the scenarios A2, A1B and B1, as continuations of the 20th century simulations. Shading is plus/minus one standard deviation range of individual model annual averages. Trenberth/IPCC

Constant 2000 CO2Constant 2000 CO2

Emissions

High

Medium

Low

Predictions of increased CO2 & Temperature

Missing Carbon

Sink

• CO2 is accumulating in the atmosphere more slowly than expected (believe it or not)

• Based on our understanding of CO2 emissions and ocean and atmosphere uptake, there is a missing sink/uptake of about 25% NASA OCO mission

Woods Hole web page

Ocean Carbon Uptake

QuickTime™ and aTIFF (LZW) decompressor

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Ocean Uptake of CO2 SciAm article

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The Oceans & Global Change

• Much of this material is courtesy of

– Julia Cole, here in Geosciences at UA and – Kevin Trenberth at the National Center

for Atmospheric Research [NCAR]

QuickTime™ and aTIFF (LZW) decompressor

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Ocean Transport of Heat

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3D “Conveyor Belt” Concept

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Potential Changes Related to the Ocean

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Change in Thermohaline Circulation

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Change in Ocean Chemistry

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Ocean Acidification (SciAm article)

• Currently ~1/3 of CO2 released by burning fossil fuels ends up in the ocean.

• Absorbed CO2 forms carbonic acid in seawater, lowering the slightly alkaline pH level, changing the balance of carbonate & bicarbonate ions.

• Shift toward acidity & ensuing changes in ocean chemistry, make it more difficult for creatures to build hard parts out of calcium carbonate.

• Decline in pH thus threatens a variety of organisms, including corals, which provide one of the richest habitats on earth.

• Within a century, Southern Ocean surface will be corrosive to shells of tiny snails key in the marine food chain within this highly productive zone.

from ocean expansion and melting glaciers

from ocean expansion and melting glaciers

Since 1993 Global sea level has risen 43 mm (1.7 inches)

• 60% from expansion as ocean temperatures rise, • 40% from melting glaciers

Since 1993 Global sea level has risen 43 mm (1.7 inches)

• 60% from expansion as ocean temperatures rise, • 40% from melting glaciers

from Steve Nerem via Trenberth

Sea level is rising:

Observed Ocean Warming

• Most oceans are warming

• Figures from Hansen et al 2006

Evidence for reality of climate changeEvidence for reality of climate change

Glaciers meltingGlaciers melting

1900 2003 Alpine glacier, Austria

1909

TobogganGlacierAlaska

2000

Muir Glacier, Alaska

Today 125,000 years ago

Research indicates that less than 8°F of Arctic warming caused Greenland to lose enough water to raise sea level by up to 12 feet during the Last Interglacial Period

Image from Bette Otto-Bliesner, National Center for Atmospheric Research

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BUT, sea level rise during the Last Interglacial Period appears to have been

more… it was likely up to 21 feet.

A reduced Greenland Ice Sheet could only have contributed up to 12 feet…

Where did the rest of the water come from?

Most likely Antarctica… QuickTime™ and a

TIFF (Uncompressed) decompressorare needed to see this picture.

http://svs.gsfc.nasa.gov

East Antarctic Ice Sheet

West Antarctic Ice Sheet

Today

125,000 years ago - the West Antarctic Ice Sheet may have been gone

East Antarctic Ice SheetLate Quaternary

diatoms and anomalously high 10Be found in sediments under the ice sheet

www.gfdl.noaa.gov

1 meter

4 meters

2 meters

8 meters

Increasing melt zones.

Melt descending into a moulin: a vertical shaft carrying water to the base of the ice sheet.

NSIDC (above)Braithwaite: Univ. Manchester

Surface melt on Greenland

Greenland ice mass budget

Researchers Mass Change Method Time Span (GT/year)Krabill et al. 2000 -47 Aircraft Surveys 1994-1999Velicogna et al. 2006 -200 to -260 GRACE 2002-2006Luthcke et al. 2007* -145 to -175 GRACE 2003-2006Zwally et al. 2007* -80 to -100 ICESat 2003-2005

GRACE is a gravity recovery missionICESat is a lidar topographymission

NASA website on Greenland ice sheet

A great deal of effort is going into estimating how the Greenland ice sheet is changing

100 GT/yr ~ 0.3 mm/yr sea level rise

Snow cover and Arctic sea ice are decreasing

Snow cover and Arctic sea ice are decreasing

Spring snow covershows 5% stepwise drop during 1980s

Arctic sea ice area decreased by 2.7% per decade(Summer: -7.4%/decade)

2007: 22% (106 km2) lower than 2005

Trenberth/IPCC

Arctic sea ice disappears in summer by 2050Already 2007 lowest on record by 22%

Abrupt Transitions in Summer Sea Ice

• Gradual forcing results in abrupt Sept ice decrease

• Extent decreases from 80 to 20% coverage in 10 years.

• Relevant factors:• Ice thinning• Arctic heat transport• Albedo feedback

Trenberth from Holland et al., GRL, 2006

2007 x

Annual anomalies of global average SST and land surface air temperatureLand increased 0.4oC vs ocean suggesting 3% decrease in RH over land

SSTLand

Trenberth/IPCC

Land surface temperatures are rising faster than SSTs

Human body: sweats

Homes: Evaporative coolers (swamp coolers)

Planet Earth: Evaporation (if moisture available)

Human body: sweats

Homes: Evaporative coolers (swamp coolers)

Planet Earth: Evaporation (if moisture available)

e.g., When sun comes out after showers,

the first thing that happens is that the puddles dry up: before temperature increases.

Trenberth

Total water vaporTotal water vapor

Observations show that water vapor in LOWER troposphere is indeed increasing. Surface temperature increase: 0.6C since 1970 over global OCEANS and 4% more water vapor.

Observations show that water vapor in LOWER troposphere is indeed increasing. Surface temperature increase: 0.6C since 1970 over global OCEANS and 4% more water vapor.

Water holding capacity of atmosphere increases about 7% per oC (4% per F) increase in temperature. Water holding capacity of atmosphere increases about 7% per oC (4% per F) increase in temperature.

From Trenberth/IPCC

Since late 1970’s, ocean surface has been warming at ~0.14C/decade => ~1% WV increase/decade. Observed WV trend since 1988 is ~1.2% per decade

Water vapor increase at higher temperatures

Smoothed annual anomalies for precipitation (%) over land from 1900 to 2005; other regions are dominated by variability.

Land precipitation is changing significantly over broad areasLand precipitation is changing significantly over broad areas

Increases

Decreases

Trenberth/IPCC

Regions of disproportionate changes in heavy (95th) and very heavy (99th) precipitation

Proportion of heavy rainfalls: increasing in most land areasProportion of heavy rainfalls: increasing in most land areas

Trenberth/IPCC

• more precipitation falls as rain rather than snow, especially in the fall and spring.

• snow melt occurs faster and sooner in the spring• snow pack is therefore less• soil moisture is less as summer arrives

• more precipitation falls as rain rather than snow, especially in the fall and spring.

• snow melt occurs faster and sooner in the spring• snow pack is therefore less• soil moisture is less as summer arrives

• the risk of drought increases substantially in summer

•Along with wild fire

• the risk of drought increases substantially in summer

•Along with wild fire

Declining Snow Pack in many mountain and continental areas contributes to drought

Declining Snow Pack in many mountain and continental areas contributes to drought

Trenberth

The most important spatial pattern (top) of the monthly Palmer Drought Severity Index (PDSI) for 1900 to 2002.

The time series (below) accounts for most of the trend in PDSI.

Drought is increasing most placesDrought is increasing most places

Mainly decrease in rain over land in tropics and

subtropics, but enhanced by increased atmospheric demand with warming

Trenberth/IPCC

Rising greenhouse gases are causing climate change, and arid areas are becoming drier while wet areas are becoming wetter.

Water management:- dealing with how to save in times of excess for times of drought –will be a major challenge in the future.

Rising greenhouse gases are causing climate change, and arid areas are becoming drier while wet areas are becoming wetter.

Water management:- dealing with how to save in times of excess for times of drought –will be a major challenge in the future.

Lake Powell Trenberth

Impacts on human health and mortality, economic impacts, ecosystem and wildlife impacts

Heat waves and wild firesHeat waves and wild fires

Trenberth

Extremes of temperature are changing!

Observed trends (days) per decade for 1951 to 2003:

5th or 95th percentiles

From Alexander et al. (2006)

Extremes of temperature are changing!

Observed trends (days) per decade for 1951 to 2003:

5th or 95th percentiles

From Alexander et al. (2006)

Trenberth/IPCC

Global Atmo Energy Imbalance

Ahrens, Fig. 2.14

Solar inSolar in

AtmosphereAtmosphere

IR OutIR Outis reducedis reduced

Increasing GHG concentrations decrease Energy outSo Energy IN > Energy OUT and the Earth warms

Extreme Heat WaveSummer 2003Europe30,000 deaths

Heat waves are increasing: an exampleHeat waves are increasing: an example

Trend plus variability?

Trenberth/IPCC

Trenberth

CO2 emissions in different regions in 2000 in terms of emissions per capita (height of each block); population (width of each block); and total emissions (product of population and emissions per capita = area of block).

Source: M. Grubb, http://www.eia.doe.gov/iea/Trenberth

Trenberth