Tues Jan 6 - UW Atmospheric Sciences

A Climate Change Primer-- The Big Picture (text p. 3-11, IPCC FAR SPM p. 5-9)
Is the planet really warming up?
But don't many experts claim that the science of climate is uncertain?
Is a small temperature rise a big deal?
How could humans change the climate?
When did we discover the issue?
Couldn't the changes have natural causes?
Could some undiscovered phenomenon be to blame?
How do rainforests fit into the picture?
Was Hurricane Katrina related to global warming?
Whatever happened to global cooling?
And the ozone hole?
The questions listed here correspond to the headings in the text.
Is the planet really warming up?
This diagram and related information appear on p. 6 of the Summary for Policymakers (SPM) of the fourth
Assessment Report (FAR) of the Intergovernmental Panel on Climate Change (IPCC), which is in the
Coursepack.
Is the planet really warming up?
How do we know?
Can we trust the measurements?
From IPCC FAR SPM p. 11. The black lines represent the observations.
But don't many experts claim that the science of climate is uncertain?
There are just a few real experts who make that claim. Here are the important ones
“there is no consensus, unanimous or otherwise, about
long-term climate trends and what causes them”
“I cannot stress this enough -- we are not in a position
to confidently attribute past climate change to carbon
dioxide or to forecast what the climate will be in the
future.”
http://outside.away.com/outside/culture/200710/richard-lindzen-1.html
Richard S.Lindzen, MIT
Roy Spencer, NASA
John Christy, UAH
Patrick Michaels, U of VA, Cato Inst.
A very small fraction of climate researchers consider themselves to be skeptics. I would estimate the fraction to be on the
order of 2-3%. Credentials for these four leading skeptics are readily available on the Web. They are all PhDs and
respected scientists. Patrick Michaels is Chief Editor of the World Climate Report, accessible on the web.
But don't many experts claim that the science of climate is uncertain?
GLOBAL WARMING, SCIENCE, SCIENTISTS
31,000 Scientists Reject ‘Global Warming’ Agenda
In News, Science on May 22, 2008 at 5:25 pm
“The Oregon Petition”
Very few of the “scientists” who signed this petition were climate scientists. For details, see Wikipedia.
Is a small temperature rise a big deal?
Not a well posed question, because the temperature rise is not small.
0.7°C rise in global-mean temperature so far; enough to have noticeable impacts
Global-mean temperature is projected to rise to 2-3°C by 2100 (CO2 doubling)
Note that 1°C = 1.8°F, so we’re taling about a ~5°F temperature rise
Temperature rise expected to be larger over land than sea
Expect even larger rises if we burn all fossil fuel reserves
It’s possible that these projections could be overestimates, but it’s equally likely
that they’re underestimates. Uncertainty cuts both ways.
Not the end of the world,
but big enough to take seriously
How could humans change the climate?
The atmosphere has a large effect on the surface temperature of the Earth and other planets because it has
the ability to trap heat that would otherwise be radiated to space. These images portray the atmosphere as a
thin envelope surrounding the Earth. They all show the edge (limb) of the Earth. The blue is light scattered
by air molecules in the upper atmosphere.
In this close-up of the limb of the Earth shows, the warm colors are sunlight that has been transmitted
through the atmosphere. This cloud layers and aerosol layers are also visible.
Horiz
on
In this daytime image only the blue, scattered light is visible. The moon is just barely above
the horizon. Note the gradient from blue to black as you go up.
How could humans change the climate?
If volcanic eruptions can change the climate, why can’t humans?
The negative spike in 1991 is the signature of the eruption of. Mt. Pinatubo in the Philippines (inset). The
top curve shows global-mean surface air temperature. The middle curve is the estimated signature of the
temperature changes induced by volcanic eruptions and the lower curve is the difference or residual.
How could humans change the climate?
Human activity has already caused the Antarctic ozone hole.
Susan Solomon
More about that later
Year-by-year images of total ozone over the Southern Hemisphere. Note the growing area of purple, which
denotes very low ozone concentrations. This is the so-called “ozone hole”.
When did we discover the issue?
Measurements started by
C. David Keeling, Scripps
H
H
James Hansen congressional
testimony, summer 1988
K
1900
1950
H
2000
H in the top curve denotes the year of Hansen’s testimony, which happened to take place during a heat wave
in washington DC.
Couldn't the changes have natural causes?
What are the possible natural causes?
Couldn't the changes have natural causes?
What are the possible natural causes?
1. An increase in incoming solar radiation?
No, we’ve been monitoring the sun’s
emission using instruments on
board satellites since 1979. It’s varied
with the 11-year sunspot cycle but it
hasn’t increased.
The measurements shown here are from satellites. The record dates back to 1979. Before 1979 the sun’s
emission could be monitored only from ground-based measurements and these are contaminated by
atmospheric variability.
Couldn't the changes have natural causes?
What are the possible natural causes?
1. An increase in incoming solar radiation?
2. An absence of volcanic eruptions?
No, we can see the signature of
volcanic eruptions in the record but
they don’t explain the warming.
Same curves as in Slide #11.
Couldn't the changes have natural causes?
What are the possible natural causes?
1. An increase in incoming solar radiation?
2. An absence of volcanic eruptions?
3. A change in the Earth’s orbit?
No, orbital changes occur on a time
scale of thousands of years, not
100 years
Hence, the warming is not due to natural causes that we are familiar with.
Could some undiscovered phenomenon be to blame?
Sure, it’s possible, but...
If you had all the symptoms of a well
known, treatable disease, would you
refuse treatment because it’s possible
that they could be due to a yet
undiscovered disease?
Keep an open mind, but don’t reject obvious explanations.
How do rain forests fit into the picture?
How do rain forests fit into the picture?
Tropical forests are reservoirs of carbon. If they are destroyed, the carbon will
go into the atmosphere.
They may well be vulnerable to global warming.
They are an example of a fragile ecosystem that will be destroyed if
temperatures rise beyond a “tipping point”.
Without tropical forests, large areas of the tropics would be hotter and drier.
Was
Katrina
related
to global
warming?
WasHurricane
Hurricane
Katrina
related
to global
warming?
Satellite image of Hurricane Katrina August 28, 2005. Intense hurricanes have well developed “eyes” like the
one shown in this image.
Close-up of the eye of Hurricane Katrina.
Photo taken from a research aircraft flying through the eye of Hurricane Katrina. The photo
was taken by a UW researcher. The deep clouds surrounding the eye are referred to as the
“eye wall”.
2005 hurricane tracks. Far more storms made landfall than in a typical year.
Was Hurricane Katrina related to global warming?
Yes and No.
There is good reason to believe that greater warmth of the tropics favors the
development of more intense tropical cyclones.
It’s impossible to prove that any individual storm was due to global warming.
Records of intense Atlantic hurricanes date back to early colonial days.
Whether there’s a detectable long term trend toward more intense
hurricanes is a matter of debate.
For more, see articles in RealClimate blog.
http://www.gfdl.noaa.gov/~tk/glob_warm_hurr.html
Numbers of Atlantic hurricanes
Whatever happened to global cooling?
From an article that appeared in Newsweek in 1975.
http://firstfriday.files.wordpress.com/2007/08/newsweek-global-cooling.jpg
June 1974
Whatever happened to global cooling?
A PDF of this well written article can be viewed or downloaded from the class web
site.
1975
1979
Books published during the 1970s that made no mention of global cooling. Understanding Climate Change was a publication
of the National Research Council. Atmospheric Sciences is a textbook written by the instructor and a colleague. The plot at
bottom is from the Peterson et al. article described in the previous slide. It shows the prevalence of articles about global
warming, even during the 1970s.
And the ozone hole?
GreenhouseWarming and the Ozone Hole are separate issues
Greenhouse Warming
Ozone Hole
trapping of outgoing radiation
destruction of ozone
GHGs
global
out of control
CFCs
Antarctic
under control
but they are related.
CFCs are GHGs
Both are international, climate-related issues
We can learn from experience in dealing with the ozone hole
Greenhouse warming and the ozone hole are often confused by the public. One of the learning goals in ATMS 111
Greenhouse
and the Ozone Hole are separate issues
is to place them inWarming
context.