S.-P. Weng Dept of Geography NTNU

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Lecture 02

地球氣候系統與氣候變化面對氣候變遷應有的態度

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

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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 (1971-2000).

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.

What is climate?

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古 ( 歷史 ) 氣候研究 天氣預報 氣候預報 氣候變遷推估

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Role of Solar forcing ?

Role of episodicforcing ?

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CO2 changes seasonally over quite a large range. In addition, continuing the measurements showed that the values drift upward from one year to the next. After these discoveries, the science of the carbon cycle had changed forever. Since then, the "Keeling curve" has become the symbol of the ever-changing chemistry of the atmosphere and the associated warming of our planet.

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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 ( 藍綠藻 ), the only prokaryotic ( 初核質 ) organisms [Bacteria and Archaea ( 古菌 )] capable of oxygenic photosynthesis

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1972

1992

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Title

Body text

Deforestation: Rondonia, Brazil

•1975 -Healthy natural vegetation

•1986 -“Fishbone” pattern on the landscape indicate agriculture fields

•2000 -Agriculture continues to replace forest cover.

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(Alvarez hypothesis)

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Variability/extreme

vs.

Change

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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

variability).

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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.

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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 Change

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Abrupt climate change

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.

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 weeks.)

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. That’s why some scientists worry about a catastrophic event — like the breakup of the West Antarctic ice sheet or the collapse of the Atlantic thermohaline circulation.

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. It’s too soon to know for certain whether abrupt climate change could occur, but if it does, it’s 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 don’t reduce emissions.

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 don’t know how much of this cooling would be balanced by the simultaneous warming in the atmosphere.

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(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 Clausius–Clapeyron equation: des /es = LdT/RT2, (es : the saturation vapor pressure at temp.=T, L: latent heat of vaporization, R: gas constant.)

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 273°K, so that 7% K−1 is a reasonable approximation. (Trenberth et al. 2003, BAMS)

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May July

“Secular change of diurnal rainfall activity in Taipei”

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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.

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Ten facts about global warming1. The earth today is warming at a rate faster than in

any time in the last 1,000 years

2. It has been particularly enhanced over the past 20

years

3. Electricity generation in the US accounts for 33% of

the total global warming emissions, transportation

activities for 27%, and industrial activities for 19%

4. Temperatures are predicted to rise another 2.5 to

10.4 degrees Fahrenheit by the end of the century

5. The sea level across the globe has climbed between

4-10 inches in the past century

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Ten facts about global warming6. The Arctic sea ice has shrunk almost 40% in

recent decades, attributable in part due to global

warming

7. If the West Antarctic ice sheet were to melt, sea

level could rise by another 16 to 30 feet

8. Droughts and floods could become more frequent

9. El Nino events could become more frequent and

severe

10. Tropical diseases could expand their range into

areas further north

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Kyoto Protocol Basics1. 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 world’s biggest emitter, has pulled out,

saying Kyoto is too expensive and wrongly omits developing nations.

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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.

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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."

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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.

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We are having fun now!

A catastrophe waiting ahead!

(1) How far away are we from the waterfall?

A scientific question.

(2) When should we get out of the boat?

A political decision.

Gliding Down A RiverToward A Waterfall

30 minutesOr

30±10 minutes

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An Example of Chaos (uncertainty)

Dropping a wallet on the top of a snow hill…..

top of the hill

bottom of the hill

(from Philander’s “Is The Temperature Rising?”)

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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 system.

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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.

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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 results.

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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

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Global Change – An Explosive Growth Event ?

Global WarmingExponential Growth

(from Philander’s “Is The Temperature Rising?”)

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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 filled?

ANSWER: Day 101

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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 problem.

It is wiser to act sooner than later.

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Lessons Learned 1. Uncertainties in science are inevitable.

2. familiarize ourselves with the processes that determine Earth’s 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 whole.

4. We can, however, cause “inconvenience” to ourselves in the next several decades by continually perturbing the global climate.