What we wish to learn Today:
description
Transcript of What we wish to learn Today:
1. How has the climate changed during the very recent past?
2. What can we say about current climate change?
3. How do climate models work and what are their predictions for the future?
What we wish to learn Today:
Possible Causes of Climate ChangePossible Causes of Climate Change
Power: 4 x 1026 W 2 x 1017 W
Long-Term 1. Solar Luminosity2. Shifting Continents3. Greenhouse gases
Medium-Term 1. Orbital parameters2. Greenhouse gases
Short-Term 1. Oceans2. Sunspots3. Volcanoes 4. Greenhouse
gases
In May, 2010, the National Academies of Science reported to Congress that “the U.S. should act now to reduce greenhouse gas emissions and develop a national strategy to adapt to the inevitable impacts of climate change” because global warming is “caused largely by human activities, and poses significant risks for — and in many cases is already affecting — a broad range of human and natural systems.”
Rep. John Boozman (Arkansas): “Is man causing it, or, you know, is this a cycle that happens throughout the years, throughout the ages. And you can look back some of the previous times when there was no industrialization, you had these different ages, ice ages, and things warming and things. That’s the question.” [KTHV Little Rock, 3/10]
Rep. Roy Blunt (Missouri): “There isn’t any real science to say we are altering the climate path of the earth.” [Human Events, 4/29/09]
Sen. Tom Coburn (Oklahoma): “I am not the smartest man in the world … But I have been trained to read scientific documents, and it’s malarkey.” [Sooner Tea Party, 8/25/09]
Ron Johnson (Wisconsin): “I absolutely do not believe that the science of man-caused climate change is proven. Not by any stretch of the imagination. It’s far more likely that it’s just sunspot activity, or something just in the geologic eons of time where we have changes in the climate.” [Milwaukee Journal-Sentinel, 8/19/10]
John Raese (W. Virginia): “And if you have one volcano in the world that one volcano puts out more carbon dioxide than everything that man puts out.” [Charleston Gazette, 7/22/10]
The threat to our society from failure to recognize, slow down, and adapt to climate change is just one facet of the subset of threats that we face from the denial of science, the rise of opinions over facts, and the forced restraint of our ability and freedom to develop and use our minds.Rep. Paul Broun (Georgia): "All that stuff I was taught about evolution and embryology and the Big Bang Theory, all that is lies straight from the pit of Hell“. "You see, there are a lot of scientific data that I've found out as a scientist that actually show that this is really a young Earth… about 9,000 years old.“ Broun is on the House Congressional Science Committee.[6 October 2012, and captured on video at a Sportsmans Banquet, September 2012 – video http://www.youtube.com/watch?v=Ge64kMFoQEo ]
Neil Newhouse, political pollster, “We’re not going to let our campaign be dictated by fact checkers.” [NY Times, Kevin M. Kruse, published 5 Nov 2012]
2012 Texas Party platform opposes “the teaching of … critical thinking skills and similar programs that … have the purpose of challenging the student's fixed beliefs and undermining parental authority.”[NY Times, Kevin M. Kruse, published 5 Nov 2012]
North Carolina's Senate legislation (HB 819) that would have required the state's Coastal Resources Commission to base predictions of future sea level rise along the state's coast on a steady, linear rate of increase. {That is, to deliberately ignore the science indicating that sea-level rise has been and will be non-linear, rising more quickly over time as ice sheets melt}[Science Insider, by Jane J. Lee on 3 July 2012, http://news.sciencemag.org/scienceinsider/2012/07/update-revised-north-carolina-se.html ]
Recent Trends in
TemperatureN.H
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ture
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C)
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-1
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1961-1
990 m
ean
Global Temperature
Data from thermometers
Year
Solar Activity and Solar Activity and ClimateClimate
Very few sunspots seen between 1645 and 1715
Corresponds to the time of the “Little Ace Age”
Sunspot number
Little Ice Age
http://solarscience.msfc.nasa.gov/SunspotCycle.shtml
Sunspot Number
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1750 1800 1850 1900 1950 2000Year
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Nu
mb
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of
sun
spots
Sunspot number
Sunspots increased at the same time
that global temperatures
increased
Multicollinearity!
Change in sunspot number is greater
than change in solar radiation. The change in solar radiation is only
about 0.1%, too small to account for the full temperature increase
Sunspots, solar
radiation, and
temperatureGlobal Surface Temperature 1978-2009
Pre-1991
Post-1991
VO
LCANO
!Ash on cars
Volcanic eruptions cool global temperature
Volcanoes spew out ~160x less CO2 than humans do…
Satellite troposphere temperature data
El Niño index
El Niño effect on temperature
Satellite data minus El Niño effect
Volcano effect on temperature
After removing El Niño and volcanoes
Residual Trend: 0.11°C per decade
Effects of El Niño and volcanoes on air temperatures
Pinatubo
’97-98 El Niño
Summary of Climate Forcingsin “energy” terms of Watts per
m2
Orbital variations ~ 0.5 W m-2 / century (occurs over long time scales)
Solar variation ~ 0.29 W m-2 peak-to-peak over ~2 centuries
Greenhouse Gases - past: ~ +0.0067 W m-2 / century CO2, 4050 BC to ~1000
AD ~ +0.0016 W m-2 / century CH4, 4050 BC to ~ 1500
AD ~ +0.0006 W m-2 / century N2O, 4050 BC to ~ 1000
BC
Volcanic eruptions 0 down to -10 W m-2, but short lived (a few years).
Estimated long-term mean forcing ~ -0.3 W m-2
* Current GHG emission – Doubling of CO2 ~ 4 W m-2 !
Past and Modern Changes on Earth – CO2, CH4, and temperature are
correlatedCO2
CH4
Temp.
Atmospheric CO2 concentration and temperature are correlated in the Vostok ice core
Temperature variations (ºC)
Atm
osp
heri
c C
O2 c
on
cen
trati
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(p
pm
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Glaciations
Deglaciatio
ns
Modern
Paleoclimate provides perspective on where we are headed …
IPCC Projectionsto 2100
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Types of Models:Physical Models (a desktop globe)
Statistical Models (a regression, y=mx+b)
Conceptual Models (a flow chart)
Computer Models (Global Climate Models, GCMs)
“Climate models are only sophisticated tools, not crystal balls”
“A useful model is not the one which is true, but the one that is informative”
“ …all models are wrong, some are useful”
USING MODELS TO PREDICT CLIMATE
What goes into a climate model?
Climate models work pretty well…
Rainfall [annual]
Which is observed and which is modeled ?
… but there is some
variation
Prediction of the 1997-1998 El
Nino by 6 different GCM
models shows a similar pattern
of climate changes
Models show that anthropogenic causes of temperature change explain what has already
occurred.
Courtesy W. Washington/NCAR
“Climate change” is more than an environmental issue, and is related to
adaptation and societal choices
INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (IPCC)
The models must use “scenarios” of future GHG
emissions World CO2 emissions
Gig
ato
ns o
f C
arb
on
There are many different “storylines”,
or scenarios of how much CO2 will be emitted by society in
the future
Pick your future…
Source: IPCC TAR 2001
Predictions of large climate changes even by the 2050s
Hadley Centre for Climate Prediction and Research
But, we control our destiny -- Temperature from the present day to the 2080s
Hadley Centre for Climate Prediction and Research
cUnmitigated Emissions
c
c Stabilization of CO2 at 550 ppm
Stabilization of CO2 at 750 ppm
Take Home Message:
Prediction into the future is difficult, but necessary…
Summary
1. Recent changes in Earth's paleoclimate record are likely due to shifts in ocean circulation, and the effects of greenhouse gas increases. Volcanoes have had only a small effect, and the sun spot record cannot account for the heat input needed.
2. Temperature changes and greenhouse gas abundances are correlated. Rapid global warming is underway and models have been developed to predict the effects of these changes.
3. Global Climate Models (GCMs) are sophisticated tools that predict a much altered climate on Earth during the next century.