Transcript Climate_models_2012 - The Global Change Program at the

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?
Possible Causes of Climate Change
Long-Term
1. Solar Luminosity
2. Shifting Continents
3. Greenhouse gases
Medium-Term
1. Orbital parameters
2. Greenhouse gases
1.
2.
3.
4.
Power: 4 x 1026 W
Short-Term
Oceans
Sunspots
Volcanoes
Greenhouse gases
2 x 1017 W
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.”
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]
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]
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]
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]
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 sealevel 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-northcarolina-se.html ]
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]
N.H. Temperature
(°C)
2
1
Recent Trends
in Temperature
0
-1
Departures in temp (deg C)
from 1961-1990 mean
1000
1200
1400
1600
Year
1800
2000
Global Temperature
Data from thermometers
Year
Solar Activity and Climate
Sunspot number
Little Ice Age
Very few sunspots seen between 1645 and 1715
Corresponds to the time of the “Little Ace Age”
Sunspot number
Sunspot Number
250
Multicollinearity!
of ofsunspots
NumberNumber
Sunspots
200
150
100
50
Sunspots increased at
the same time that
global temperatures
increased
0
1750
1800
1850
1900
Year
1950
2000
Year
http://solarscience.msfc.nasa.gov/SunspotCycle.shtml
Sunspots, solar
radiation, and
temperature
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
Global Surface
Temperature
1978-2009
Ash on cars
Pre-1991
Post-1991
Volcanic eruptions cool global temperature
Volcanoes spew out ~160x less CO2 than humans do…
Effects of El Niño and volcanoes on air temperatures
’97-98 El
Niño
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
Pinatubo
Residual
Trend: 0.11°C
per decade
Summary of Climate Forcings
in “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 correlated
CO2
Temp.
CH4
Atmospheric CO2 concentration
and temperature are correlated in the Vostok ice core
Modern
Temperature variations (ºC)
6
Paleoclimate provides
perspective on where we
are headed …
5
4
Global
Temperature
(°C)
3
N.H. Temperature
(°C)
2
1
1
0.5
0
-0.5
1000 1200 1400 1600 1800 2000
0
IPCC Projections
to 2100
USING MODELS TO PREDICT CLIMATE
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”
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
There are many
different
“storylines”, or
scenarios of how
much CO2 will be
emitted by
society in the
future
Gigatons of Carbon
World CO2 emissions
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
c
Stabilization
of CO2 at
750 ppm
c
c
Unmitigated
Emissions
Hadley Centre for Climate
Prediction and Research
Stabilization of
CO2 at 550 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.