Download Radiation

Human Influence on Weather/Climate
 Certainties:
– We are causing a rapid rise in atmospheric CO2
 Fossil fuel burning
 Destruction of forests
– Cities are warmer, on average, than their suburbs
 Urban Heat Island
 Increased emission of heat (cars, people)
 Changes in water cycling
 Changes in surface area and
heat capacity
– We have destroyed a significant
amount of stratospheric ozone
– Higher global temperatures have
correlated with increasing CO2
Caution! Know Your Axes!
The perceived slope of a graph means less than you might think!
-- Scale of Y-Axis
-- Maximum slope with small range
-- Minimum slope with large range
-- What would graph to left look like if the scale was
from 0 to 400?
-- Scale of X-Axis
-- Same idea- spread it out, decrease the slope
Be sure you’re comparing “apples to apples” when looking at
more than one graph!
Land Use Changes
 The Dust Bowl
– Prairie grass was plowed under and overgrazed
– With no grass to hold the soil in place, a naturally occurring
prolonged dry spell (drought) caused the bare soil to be
carried away by the wind; lack of wind breaks (trees)
 The Middle East
– Biblical reference to the tall cedars of Lebanon
– Forests cut down, water cycling changed
 Trees/plants retain water, so more runs out of local area
 Transpiration: release of water vapor
by plants is
reduced; water
cycle altered
The Urban Heat Island: The Ultimate
Land Use Change
 Localized climate change: T (city) > T (rural)
– Water Cycling: Increased runoff = warmer daytimes
(less cooling due to evaporation)
– Increased surface area = more solar radiation can
be absorbed, more IR emitted and re-absorbed at
night; also higher heat capacity building materials
– Autos, factories,
people emit heat
The Urban Heat Island: The Ultimate
Land Use Change
Temperature contours
(isotherms) around a city
show an “island” of warmth
compared to the surrounding more rural areas.
Ozone Depletion: Why We Care
 Ozone protects us from high-energy (short
wavelength) UV radiation from the sun
 Measured in Dobson Units. Decreases in ozone will
cause increases in skin cancer, and ozone levels have
generally been decreasing.
Ozone Depletion: Why it’s Happening
 Ozone is a highly toxic gas, which means it can be
good or bad, depending upon where it is
 Good: In the stratosphere, where it protects us from much of the
sun’s harmful ultraviolet radiation, which causes skin cancer
 Bad: In the troposphere, where we are- it is poisonous!
 Chlorofluorocarbons destroy ozone very efficiently
Ozone Depletion: There is Hope
 CFCs destroy ozone very efficiently
– Destruction greatest in high latitudes
– Have been banned and atmospheric CFC levels
are leveling off
– As atmospheric CFC levels decline, stratospheric
ozone should recover, but there is a significant delay
between CFC reduction and ozone recovery (~60 years)
Ozone Depletion: Problem Solved?
• CFCs have been replaced by HCFCs and HFCs, which are
not as harmful to the ozone layer but are potent greenhouse
gases
• Montreal Protocol
Ozone Depletion: Ozone “Hole”
 Ozone “hole” is an area over the south pole where
stratospheric ozone levels have drastically fallen
– Atmospheric conditions (extreme cold, polar vortex) lead to
efficient ozone destruction: polar stratospheric clouds (PSC)
– Winter/spring occurrence
– Not as dramatic over the
north pole
Looks like ozone depletion
has reached a maximum
and ozone levels are
increasing/improving, ever
so s l o w l y…
…but 2015 data
show that in any
given year there can
be setbacks.
A World Avoided…
From Douglass, Newman & Solomon, The Antarctic Ozone Hole, an Update
Global Warming: The Enhanced
Greenhouse Effect
 The Greenhouse Effect keeps our planet about 60F
warmer than it otherwise would be. Life as we know it
depends upon this effect. Greenhouse gases
(primarily water vapor and carbon dioxide) absorb/reemit IR radiation.
 Enhanced Greenhouse Effect is
“Global Warming”
– Too much of a “good” thing
– Anthropogenic (human-induced)
 CO2: correlates well with temp.
 Methane
 CFCs – low concentrations, but
very efficient IR absorbers
http://www.skepticalscience.com/co2-measurements-uncertainty.htm
http://www.skepticalscience.com/trend_and_variation.html
http://www.globalchange.gov/browse/multimedia/earths-temperature-variations
Methane: another player
Temperature data
source: NASA
What about cooling I’ve heard about? (PDO)
Global Decadal Temperatures
Global temperatures continue to
climb. The 2010s are warmer
than the 2000s
http://www.chron.com/news/science-environment/article/Video-NASA-timelapse-footage-shows-Arctic-Sea-10424673.php
Global Warming: Some Uncertainties
 Cloud cover: Should increase as temperature and condensation
nuclei (pollution) increase, but type of cloud has an effect on
surface temperature. Some cause cooling, some cause
warming. Which type will increase more? Climate models still
struggle with cloud prediction.
 Sea Level changes: Expected to rise as snow/ice melts, and as
water warms (and expands), and is happening now, but some
regions will see increased snowfall if planet warms, offsetting
some, but not all of the sea level rise
– Recent dramatic cooling of top 2,500ft ocean layer
– More recent work on this ocean “cooling”
– Island nations especially concerned
 Ocean Currents: Infusion of fresh water alters density, disrupts
currents; local climate changes
(warming and cooling)
 Climate change: Gradual or Rapid?
– “slipping” glaciers lubricated by meltwater
Sea Level Rise
 Thermal Expansion
 Icecaps and Glaciers (Greenland)
Global Warming: Other Uncertainties
 Political Forces
– Will countries play by the rules after ratifying a
treaty? (Not happening for many countries now)
– Should developed countries curtail their emissions
and let developing nations continue until their
emissions become “substantial?”
– Should developing nations be denied the chance
the U.S. and other developed nations had?
 No, it’s only fair. We can’t stifle their development
 Yes, we know more today about what we’re doing to the
planet
– Then, should developed nations cover the increased cost
developing nations will incur to meet stricter environmental
guidelines? After all, we screwed it up in the first place.
– Carbon credit trading
Why Climate Scientists and Environmentalists Worry
(but why I think there is hope)…
Note: This article is certainly critical of his views, but even though I’m concerned I am not convinced
he’s unwilling to hear more about the science. Read carefully and keep an open mind…
On Jan. 18, after Sanders had attacked Trump’s climate change views in the Democratic
debate, Trump told Fox & Friends, "Well, I think the climate change is just a very, very
expensive form of tax. A lot of people are making a lot of money. I know much about
climate change. I'd be — received environmental awards. And I often joke that this is
done for the benefit of China. Obviously, I joke. But this is done for the benefit of China,
because China does not do anything to help climate change. They burn everything you
could burn; they couldn't care less. They have very — you know, their standards are
nothing. But they — in the meantime, they can undercut us on price. So it's very hard on
our business."
Trump may call the mention of China’s role a joke, but he certainly has a lengthy record
of using the word "hoax" to describe climate change. On Dec. 30, 2015, Trump told the
crowd at a rally in Hilton Head, S.C., "Obama's talking about all of this with the global
warming and … a lot of it's a hoax. It's a hoax. I mean, it's a money-making industry,
okay? It's a hoax, a lot of it."
That’s three times using "hoax" in one sentence. Trump has also used the word on
Twitter since his 2012 tweet.
On Jan. 25, 2014, Trump tweeted, "NBC News just called it the great freeze — coldest
weather in years. Is our country still spending money on the GLOBAL WARMING
HOAX?"
Paris Accord: Dead or Alive?
And Finally…..
Thinking about what it was like to
be very dependent upon others
for our energy needs and
recognizing how things have
changed, are we better off now?
 “And finally, most important of all, basing an economy on a
commodity that [in my opinion] is controlled by the most
backward, unstable, and violent countries in the world is
madness.” (2006, but still relevant)
- Craig Bohren, in USA Today
 Now we have fracking. So, is cheap energy and the
potential for energy independence necessarily a good
thing?
Key Figures
 READ CHAPTER 18, it’s all important