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Climate variability and climate change


Lecture 01 Climate variability and climate change Greenhouse effect and global warming – PowerPoint PPT presentation

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Title: Climate variability and climate change

Lecture 01??????????????????????
  • Climate variability and climate change
  • Greenhouse effect and global warming
  • Arguments concerning climate change
  • Kyoto Protocol basics
  • IPCC conclusions
  • Natural vs. anthropogenic climate variability

What is climate?
  • ? Narrow sense Average weather
  • ? Wider sense State of the climate system
  • State Statistical description in terms of the
    mean and variability (at least) of relevant
    quantities over a period of time (months,
    several, thousands, or millions of years) over a
    certain area. The classical period is 30 years,
    as defined by the WMO (1961-1990), IPCC
  • Climate system complex system consisting of
    five major subsystems atmosphere, hydrosphere,
    cryosphere, land surface and the biosphere, and
    the interactions/feedbacks of the atmosphere and
    the change of land-use.

?(??)???? ???? ???? ??????
Role of Solar forcing ?
Role of episodicforcing ?
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Many believe that O2 concentration underwent a
dramatic increase between 2.2 and 2.4 billion
years ago and was produced initially by
cyanobacteria (??? ), the only prokaryotic (??? )
organisms Bacteria and Archaea (?? ) capable of
oxygenic photosynthesis
Deforestation Rondonia, Brazil
Body text
  • 1975 -Healthy natural vegetation
  • 1986 -Fishbone pattern on the landscape
    indicate agriculture fields
  • 2000 -Agriculture continues to replace forest

(Alvarez hypothesis)
Variability/extreme vs. Change
  • What is Climate Variability?
  • Variations in the mean state and other higher
    order statistics (such as standard deviations,
    variances, and occurrences of extremes, etc.) of
    the climate on all temporal and spatial scales
    beyond that of individual weather events.
  • Variability may be due to either natural internal
    processes within the climate system (i.e.
    internal variability) or to variations in natural
    or anthropogenic external forcing (external

  • What is Climate Change?
  • Statistically significant variation in either the
    mean state of the climate or in its variability,
    persisting for an extended period (typically
    decades or longer).
  • Climate change may be due to natural internal
    processes or external forcings, OR to persistent
    anthropogenic changes in the composition of the
    atmosphere OR in the land use.

UNFCCC makes a distinction between climate
change attributable to human activities altering
the atmospheric composition, AND climate
variability attributable to natural causes (both
internal and external).
United Nations Framework Convention on Climate
The National Research Council recommends that
more research should be focused on understanding
the mechanisms that lead to abrupt climate
changes, and special attention paid to providing
realistic estimates of the likelihood of such
extreme events.
Abrupt climate change
Development of EVT in statistical community
Movie scenario. Temperatures in New York City
change from sweltering to freezing in
hours.Actual climate change. Temperatures in
parts of the world could drop, but not nearly as
rapidly or dramatically as portrayed in the
movie. In a warmer world, additional rain at
middle and high latitudes, plus melt from
glaciers, will add more fresh water to the
oceans. This could affect currents, such as the
Gulf Stream, that transport heat north from the
tropics and might result in parts of North
America and Europe becoming relatively cooler.
Even if this were to occur, it would take many
years or decades because oceans move heat and
cold much more slowly than the atmosphere. (Some
ocean changes, however, such as the periodic
warming of Pacific Ocean waters known as El Niño,
may affect regional weather patterns within
Movie scenario. A massive snowstorm batters New
Delhi as an ice age advances south.Actual
climate change. Although human-related emissions
of carbon dioxide and other greenhouse gases
might cool some parts of Earth by affecting ocean
currents, they cannot trigger a widespread ice
age. That is because increased levels of
greenhouse gases will increase temperatures
across much of the planet. In addition, Earth's
orbit is in a different phase than during the
peak of the last major ice age 20,000 years ago,
and the Northern Hemisphere is receiving more
solar energy in the summer than would be
associated with another ice age.
Movie scenario. Tornadoes strike Los Angeles and
grapefruit-sized hail falls on Tokyo.Actual
climate change. Research has shown that climate
change might lead to more intense hurricanes and
certain other types of storms. In a hotter world,
evaporation will happen more quickly, providing
the atmosphere with more fuel for storms. In
fact, scientists have found this is already
happening with rain and snowfall in the United
States. But even when scientists run scenarios on
the world's most powerful supercomputers, they
cannot pinpoint how climate will change in
specific places or predict whether Los Angeles or
other cities will face violent weather.
What is an abrupt climate change?When scientists
talk about climate change, they are usually
referring to gradual climate change. In other
words, if the planet warms steadily, the climate
changes steadily. But there's evidence that some
parts of the climate system work more like a
switch than a dial if a certain temperature
level is reached, there may be an abrupt and
large change in the climate. Thats why some
scientists worry about a catastrophic event
like the breakup of the West Antarctic ice sheet
or the collapse of the Atlantic thermohaline
Could an abrupt climate change really
happen? Scientists have just begun to study the
possibility of an abrupt climate change. But when
scientists talk about abrupt climate change, they
mean climate change that occurs over decades,
rather than centuries. Its too soon to know for
certain whether abrupt climate change could
occur, but if it does, its not expected to
happen within the next several decades.
Do scientists agree about global
warming? Although scientists still argue about
how fast and how much the atmosphere will warm,
the mainstream scientific community agrees on 3
key points 1. the earth is warming 2. the
warming can only be explained by the build-up of
greenhouse gases in the atmosphere and that 3.
the warming will continue if we dont reduce
How can global warming cause cold
weather? Without the thermohaline circulation,
not as much heat would be transported from the
tropics to the North Atlantic region. Eastern
North America and Western Europe would cool,
while the rest of the world continues to warm. We
dont know how much of this cooling would be
balanced by the simultaneous warming in the
(a) Increase the mean
(b) Increase variance
(c) Increase both mean and variance
Water-holding capacity in atmosphere is governed
by C-C relationship
  • The ClausiusClapeyron equation des /es
    LdT/RT2, (es the saturation vapor pressure at
    temp.T, L latent heat of vaporization, R gas
  • Changes in saturation-specific humidity also
    involve the ratio of the gas constant of dry air
    to that of water vapor (0.622) range from 6.0
    K-1 at 300 K to 7.4 K-1 at 270 K.
  • Global mean temperatures at 850 and 700 hPa are
    about 280 and 273K, so that 7 K-1 is a
    reasonable approximation. (Trenberth et al. 2003,

Secular change of diurnal rainfall activity in
  • Climate Change detection and attribution
  • Detection of climate change is the process of
    demonstrating that climate has changed in some
    defined statistical sense, without providing a
    reason for that change.
  • Attribution of causes of climate change is the
    process of establishing the most likely causes
    for the detected change with some defined level
    of confidence.

  • Ten facts about global warming
  • The earth today is warming at a rate faster than
    in any time in the last 1,000 years
  • It has been particularly enhanced over the past
    20 years
  • Electricity generation in the US accounts for 33
    of the total global warming emissions,
    transportation activities for 27, and industrial
    activities for 19
  • Temperatures are predicted to rise another 2.5 to
    10.4 degrees Fahrenheit by the end of the century
  • The sea level across the globe has climbed
    between 4-10 inches in the past century

  • Ten facts about global warming
  • The Arctic sea ice has shrunk almost 40 in
    recent decades, attributable in part due to
    global warming
  • If the West Antarctic ice sheet were to melt, sea
    level could rise by another 16 to 30 feet
  • Droughts and floods could become more frequent
  • El Nino events could become more frequent and
  • Tropical diseases could expand their range into
    areas further north

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Kyoto Protocol Basics 1. What is the Kyoto
Protocol? It's a pact agreed by government
delegates at a 1997 U.N. conference in Kyoto,
Japan, to reduce the amount of greenhouse gases
emitted by developed countries by 5.2 percent of
1990 levels during 2008-2012. A total of 141
nations have ratified the pact, according to U.N.
data. 2. Is it the first agreement of its
kind? Governments originally agreed to tackle
climate change at the 1992 Earth Summit in Rio de
Janeiro. At that meeting, leaders created the
UNFCCC, which set a non-binding goal of
stabilizing emissions at 1990 levels by 2000, a
goal not met overall. The Kyoto protocol is the
follow-up to that and is the first legally
binding global agreement to cut greenhouse
gases. 3. Is it legally binding? had legal force
for its participants since Feb. 16 (2005) after
meeting twin conditions -- backing from at least
55 countries and support from nations
representing at least 55 percent of developed
countries carbon dioxide emissions. It passed
the second hurdle in November 2004 when Russia
ratified and now has backing from nations
representing 61.6 percent of emissions. The
United States, the worlds biggest emitter, has
pulled out, saying Kyoto is too expensive and
wrongly omits developing nations.
4. How will it be enforced? Under a 2001 deal
made by environment ministers, if countries emit
more gases than allowed under their targets at
the end of 2012, they will be required to make
the cuts, and 30 percent more, in the second
commitment period, which is due to start in 2013.
They rejected the idea of a financial penalty. 5.
Must all cut emissions by 5.2 percent? No, only
39 countries -- relatively developed ones -- have
target levels for the 2008-12 period, adhering to
a principle that richer countries should take the
lead. Each country negotiated different targets,
with Russia aiming for stabilization at 1990
levels and the European Union taking an 8.0
percent cut. 6. How are supporters doing so
far? Many countries are lagging behind Kyoto
targets. Emissions by Spain and Portugal were
40.5 percent above 1990 levels in 2002. U.S.
emissions were up 13.1 percent. Emissions by
ex-communist bloc states fell most sharply due to
the collapse of Soviet-era industries -- Russian
emissions were down 38.5 percent.
7. How will countries comply? The European Union
set up a new market in January 2005 under which
about 12,000 factories and power stations are
given carbon dioxide quotas. If they overshoot
they can buy extra allowances in the market or
pay a financial penalty if they undershoot they
can sell them. Prices in the EU market are now
about 7.2 euros per metric ton. 8. What if a
country misses its target? The protocol provides
for "flexible mechanisms" -- ways for countries
to reach their targets without actually reducing
emissions at home. These include emissions
trading -- where one country buys the right to
emit from a country that has already reduced its
emissions sufficiently and has "spare" emissions
reductions. Another is the "clean development
mechanism" where developed countries can earn
credits to offset against their targets by
funding clean technologies, such as solar power,
in poorer countries.Countries can also claim
credits for planting trees in the Third World
that soak up CO2 -- carbon "sinks."
Dilemma for Policy Makers
  • How do we weight the possible harm of our
    actions against the advantage of economic growth?
  • ? Policy makers want scientists to make precise
    predictions of the timing and magnitude of the
    future global warming.

Gliding Down A River Toward A Waterfall
We are having fun now!
  • How far away are we from the waterfall?
  • ? A scientific question.
  • (2) When should we get out of the boat?
  • ? A political decision.

30 minutes Or 3010 minutes
A catastrophe waiting ahead!
An Example of Chaos (uncertainty)
Dropping a wallet on the top of a snow hill..
top of the hill
bottom of the hill
(from Philanders Is The Temperature Rising?)
  • It is important to accept that fact that
    ..although accurate predictions are, in
    principle, possible on the basis of the laws of
    physics, such forecasts may be impossible in
    practice.. because the complexity of our climate

How Should Policy Makers Cope with the
Uncertainties in Science?
  • Rather than implement comprehensive programs
    that decree a rigid course of action to reach
    grand and final solution,
  • We should promote adaptive programs whose
    evolution is determined by the results of these
    programs and by the new scientific results that
    become available.

A Successful Case of the Adaptive Approach
  • In 1987, the world agreed in the Montreal
    Protocol that each country would limit its
    production of the chlorofluorocarbons (CFCs) that
    contribute to the depletion of the ozone hole.
  • This decision was made before clear evidence
    that CFCs are harmful to the ozone layer.
  • The regulations were agreed in subject to
    periodic reviews to accommodate new scientific

Explosive Growth Events
  • A gardener finds that his pond has one lily pad
    on a certain day, two the next day, four the
    subsequent day and so on. After 100 days the pond
    is completely filled with lily pads. On what day
    was the pond half full?
  • ANSWER Day 99

Global Change An Explosive Growth Event ?
Global Warming
Exponential Growth
(from Philanders Is The Temperature Rising?)
Consequence of Late Response
  • Suppose the gardener, once he realizes what is
    happening, quickly enlarge the pond to twice its
    size. On what day will the new pond be completely
  • ANSWER Day 101

Sooner Is Better Than Later
  • Is our global warming problem close to Day 1 or
    Day 100? (This is a scientific problem)
  • Instead of waiting for a precise answer to end
    this debate, it is more important to recognize
    the explosive-growth nature of the global warming
  • It is wiser to act sooner than later.

Lessons Learned
  • 1. Uncertainties in science are inevitable.
  • 2. familiarize ourselves with the processes that
    determine Earths climate and the sensitivity of
    these processes to perturbations.
  • 3. Over tens of thousands of years, we are
    unlikely to do great harm to our planet as a
  • 4. We can, however, cause inconvenience to
    ourselves in the next several decades by
    continually perturbing the global climate.

Should we worry about global warming?Global
temperatures have increased by 1 degree
Fahrenheit over the past 100 years. Although this
may seem like a small change, it is enough to
harm important ecosystems, change rainfall
patterns and raise the sea level. Climate models
project additional warming of about 2-10 F over
the next 100 years. The overwhelming consensus of
scientists who study the atmosphere is that this
warming is caused primarily by the build-up of
greenhouse gases in the atmosphere, mostly from
the burning of fossil fuels like coal and oil.
What is the Atlantic thermohaline
circulation?The Atlantic thermohaline
circulation, which includes the Gulf Stream, acts
like an oceanic conveyer belt that carries heat
from the tropics to the North Atlantic region.
Warm surface water from the tropics travels
northward by the Gulf Stream. As the warm water
cools in the North Atlantic, it sinks to the
ocean floor, and then slowly moves southward
until it returns once again to the tropics. This
ocean circulation pattern is caused by
differences in water temperature and salinity in
the ocean.
Could climate change shut down the thermohaline
circulation?Global warming is expected to
increase ocean temperatures and to increase the
flow of freshwater into the ocean through
precipitation, run-off, and melting of glaciers.
Many climate models have projected that increased
surface ocean temperatures and reduced salinity
could slow or completely shut down the
thermohaline circulation.
What are the chances of the thermohaline
circulation shutting down?We dont yet know the
probability of the thermohaline circulation
shutting down. It depends on how much and how
quickly the atmosphere warms. In general, it is
considered possible but not very likely. If it
were to occur, it would probably not happen
within the next 100 years, and circulation would
eventually recover, after decades or centuries.
If The Day After Tomorrow is fiction, what is
the truth about global warming?The truth is that
global warming is happening and that it is
already too late to avoid some of the effects.
Even under the most optimistic circumstances,
atmospheric scientists expect global climate
change to result in increased flooding and
droughts, more severe storms, and a loss of plant
and animal species. These events will occur, even
if climate change is gradual.
What can be done about global climate
change?There is no single cause of global
climate change and there is no single solution.
Most experts believe that technology will provide
solutions. Technologies that reduce emissions
(energy efficiency, hydrogen fuels, carbon
storage, nuclear energy and renewable energy) and
technologies that remove carbon from the
atmosphere may all play a role. Government
policies that encourage businesses to develop and
use these and other technologies are also very
important. Many states and businesses have
already found that they can reduce emissions
while saving money.
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