Slide1 : Peter H. Hildebrand, Ph.D. Climate Change and Ecosystems Hydrospheric and Biospheric Sciences Laboratory NASA Goddard Space Flight Center, Greenbelt, MD
Slide2 : Climate, Water and Life on Earth Earth’s climate:
natural and
human forces
of change
Earth’s water cycle in a
changing climate Ecosystem
impacts Actions
we can take
Slide3 : 100 100 Incoming
Solar Radiation Outgoing Earth
Radiation Earth’s Heat Budget Incoming and outgoing radiation must balance
The atmosphere, clouds, and greenhouse gases keep us warm.
Greenhouse Gas and Human Activity : Greenhouse gases are natural:
H2O, CO2, CH4, . . .
Humans add more greenhouse gases
These gases are warming the Earth Greenhouse Gas and Human Activity
How do we know about Greenhouse Gases? : How do we know about Greenhouse Gases? Greenhouse gas concept known since 1820s:
Joseph Fourier (1824, 1927)
John Tyndall (1861)
Svante Arrhenius (1896)
David Keeling measured CO2 on top of Mauna Loa
CO2 is increasing each year
winter summer High CO2 values = northern winter
Low CO2 values = northern summer, (when trees are growing)
Radiative Forcing of Climate Change : Radiative Forcing of Climate Change Climate Change Forcing in the Industrial Era (1850-2000)
► CO2 Is Largest Forcing
► Air Pollutants (O3, CH4, BC) Cause Large Forcing
► Aerosol Effects (direct + on clouds) Most Uncertain
Conclusion: CO2 Largest Forcing, But Others Significant
References:
►Trends of measured climate forcing agents, Proc.Natl.Acad.Sci., 98, 14778, 2001.
►Efficacy of climate forcings, J. Geophys. Res., in press, 2005.
Slide7 : Climate Variability: Global Temperature
How do we know about greenhouse gas history?Climate records from polar ice cores : The history of Earth climate is available from Antarctic and Greenland ice cores.
Temperatures from oxygen isotope ratios.
Greenhouse gases from air bubbles trapped in the ice cores.
Other measurements validate these records. How do we know about greenhouse gas history? Climate records from polar ice cores
Climate Change: variability over 450,000 years : Climate Change: variability over 450,000 years Ice Ages
(cold, dry, windy) Warm periods
(warm, wet, calm) greenhouse
gases change
in response
to climate
change Last 150yrs:
greenhouse
gases driving
temperature
change
The Water Cycle and Climate : Terrestrial water cycle
Precipitation
Storm and drought intensity
Snowfall
Runoff
Tropical storms
Global ice
Ice sheets and glaciers / sea ice
Sea level The Water Cycle and Climate As the Earth has warmed,
what has happened to Earth’s water resources ?
Slide11 : Where has the Earth warmed? Hotter Equator
Changes in Precipitation : Changes in Precipitation Less Rain More Rain
Precipitation Intensity Increases : Precipitation Intensity Increases More days with precipitation
More frequent and intense precipitation
Precipitation increases are due to the strong events
Snow Cover Reduced : Snow Cover Reduced As temperatures increase:
Snow cover reduced 1-2 days/yr since early 1970’s
Water storage in snow pack is reduced
More precipitation is rain
Snow onset is later
Melt is earlier
Slide15 : days/yr The Water Cycle and Climate Runoff Changes With a warmer land and atmosphere:
Runoff changes:
More precipitation falls as rain
Winter runoff is increased
Winter starts later & ends earlier
Spring runoff pulse is earlier
Summer runoff is decreased
Slide16 : Tropical Storms Orange colors indicate where SST’s will support Tropical Cyclone Development SST ≥ 82°F
Hurricane Intensity Increases : Hurricane Intensity Increases Hurricane intensity changes:
fewer category 1 storms
more cat 4 and 5 storms Sea surface temperatures
are increasing globally
Polar Ice Sheets : Polar Ice Sheets Changes in polar ice:
Ice sheets
Sea ice
Ecosystem impacts
Sea level impacts
Antarctica: Melting and Thickening : Antarctica: Melting and Thickening Thickening
due to increased
precipitation Melting around
the edges
Greenland: Melting : Greenland: Melting
The Water Cycle and Climate : Precipitation:
More & Heavier events
Storm intensity
Stronger large scale weather patterns:
More intense heavy precipitation & drought
More intense storms including hurricanes
Snowfall decrease
Later freeze, earlier thaw
More precipitation as rain
Earlier runoff
Melting of ice sheets and glaciers
Sea level rise The Water Cycle and Climate With a hotter Earth, what has happened to water resources?
Ecosystem Impacts:Melting Ice in the Arctic : Ecosystem Impacts: Melting Ice in the Arctic
Ecosystem Impacts: What does this mean for a farmer? : Ecosystem Impacts: What does this mean for a farmer? He is concerned about climate change effects:
Getting enough water from the river (snow melt) for irrigation
Getting water in the summer
Reservoir management
Urban encroachment
Climat Change and the Water Cycle Why are scientists concerned? : The Earth system is replete with tipping points:
small changes that cause big effects Climat Change and the Water Cycle Why are scientists concerned? Examples of Causes and effects:
Earth orbit variability ice-age climate cycle
Arctic Melting Ocean circulation slows
Tipping Points: Ice Ages vs. Interglacial Periods : Tipping Points: Ice Ages vs. Interglacial Periods Ice Ages
(cold, dry, windy) Warm periods
(warm, wet, calm) greenhouse
gases change
in response
to climate
change Last 150yrs:
greenhouse
gases driving
temperature
change
Climate over the past 450,000 years:Ice ages, brief warm spells, & lots of variability : Climate over the past 450,000 years: Ice ages, brief warm spells, & lots of variability Earth-sun orbital cycles (causative):
eccentricity, precession, nutation
Earth circulation variability (causative):
E.g. el Niño; also, longer scale major variability
Greenhouse gases:
were in reaction to Earth circulation / temperature changes
now a causative factor What makes the climate change?
Tipping Points: Polar Melting & Global Heat Transport : Global warming feedback loop:
Reduced snow/ice cover
albedo is reduced
solar heating is increased
tundra & permafrost thaw
more greenhouse gases released
Melted ice sheets
release fresh water into ocean
fresh water dilutes cold salty North Atlantic water
shuts down the North Atlantic circulation
this changes global heat transport
This climate “switch” has been thrown many times! Tipping Points: Polar Melting & Global Heat Transport
Slide28 : Climate models are now pretty good.
A major uncertainty is:
What are we humans going to do?
IPCC “Emissions Scenarios”
A2: heterogeneous world, continued population growth
A1B: rapid economic growth, homogeneous world,
population peaks ~2050, mixed fossil/non-fossil fuel use
B1: =A1 with global sustainability and equity focus Climate Forecasting
Slide29 : Climate Forecasting more less People,
Development & Pollution
Slide30 : Climate Change and Societal Decisions
Slide31 : Climate Change and Societal Decisions Society can make choices that will affect our environment Present averaged heating due to greenhouse gases Possible future heating: need to limit the amount of heating
What can we do?Change how we live: reduce energy use emphasize sustainability reduce population growthChange our technology: improve energy use efficiency : What can we do? Change how we live: reduce energy use emphasize sustainability reduce population growth Change our technology: improve energy use efficiency
Thank you! : Thank you! For more information
please visit
http://neptune.gsfc.nasa.gov/
The Water Cycle and Climate Human water use 1900 – 2000 : The Water Cycle and Climate Human water use 1900 – 2000
Slide35 : The Water Cycle and Climate Human water use: Grain Production
Slide36 : Grain Production
Slide37 : For more information
Books:
Richard Alley: The Two–Mile Time Machine. A very readable climate change book for the lay reader written by a noted Penn State Prof.
Brian Fagen: The Long Summer. A discussion of how the warming at the end of the last ice age fostered the development of human civilization.
Jared Diamond: Collapse. As Diamond says: how societies choose to fail or succeed.
Malcolm Gladwell: The Tipping Point. A discussion of how small factors can sometimes result in large changes.
Web Resources:
Climate science web site: www.realclimate.org
US Global Change Research Program: www.usgcrp.gov
UN Environmental Program: www.unep.org
NASA Earth Sciences: earthsciences.gsfc.nasa.gov
Goddard Hydrospheric & Biospheric Sciences: neptune.gsfc.nasa.gov
NASA Goddard Climate Sciences: www.giss.nasa.gov
Climate change figures: www.grida.no/climate/vital/index.htm
USDA Foreign Agricultural Service: www.fas.usda.gov/grain/circular/2004/05-04/graintoc.htm
Worldwatch: www.worldwatch.org
Climate, Water and Life on Earth Peter H. Hildebrand, Ph.D., NASA Goddard
Climate Change and Desertification : Climate Change and Desertification NDVI = (ir- red) (ir+red) NDVI measures plant greenness The Sahel Movement with climate change
How might warming affect the global water cycle? : How might warming affect the global water cycle? 38 38 105 67 393 355 1000 km3/yr