Lecture 01 Climate variability and climate change l

Lecture 01 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 l Greenhouse effect and global warming l Arguments concerning climate change l Kyoto Protocol basics l IPCC conclusions l Natural vs. anthropogenic climate variability l S. -P. Weng Dept of Geography NTNU 1

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 (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. S. -P. Weng 2

Role of episodic forcing ? S. -P. Weng Role of Solar forcing ? 4

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Many believe that O 2 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 S. -P. Weng prokaryotic (初核質 ) organisms [Bacteria and Archaea (古菌 )] capable of oxygenic 10 photosynthesis

1972 1992 S. -P. Weng 11

Title Deforestation: Rondonia, Brazil Body text • 1975 -Healthy natural vegetation • 1986 -“Fishbone” pattern on the landscape indicate agriculture fields • 2000 -Agriculture continues to replace forest cover. S. -P. Weng 12

(Alvarez hypothesis) S. -P. Weng 13

Variability/extreme vs. Change S. -P. Weng 14

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). S. -P. Weng 15

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. S. -P. Weng 16

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 S. -P. Weng 17

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. Abru pt cl S. -P. Weng imat e ch ange Development of EVT in statistical community 18

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 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.

(a) Increase the mean (b) Increase variance (c) Increase both mean and variance S. -P. Weng 26

Water-holding capacity in atmosphere is governed by C-C relationship The Clausius–Clapeyron equation: des /es = Ld. T/RT 2, (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 h. Pa are about 280° and 273°K, so that 7% K− 1 is a reasonable approximation. (Trenberth et al. 2003, BAMS) S. -P. Weng 27

“Secular change of diurnal rainfall activity in Taipei” May S. -P. Weng July 28

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. S. -P. Weng 29

Ten facts about global warming 1. 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 S. -P. Weng 30

Ten facts about global warming The Arctic sea ice has shrunk almost 40% in recent decades, attributable in part due to global 6. 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 S. -P. Weng 31

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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 world’s biggest emitter, has pulled out, S. -P. Weng saying Kyoto is too expensive and wrongly omits developing nations. 33

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 Sovietera industries -- Russian emissions were down 38. 5 percent. S. -P. Weng 34

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 CO 2 -- carbon "sinks. " S. -P. Weng 35

Dilemma for Policy Makers l 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. S. -P. Weng 36

Gliding Down A River Toward A Waterfall We are having fun now! (1) 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 30± 10 minutes S. -P. Weng A catastrophe waiting ahead! 37

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? ”) S. -P. Weng 38

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. S. -P. Weng 39

How Should Policy Makers Cope with the Uncertainties in Science? l Rather than implement comprehensive programs that decree a rigid course of action to reach grand final solution, l We should promote adaptive programs whose evolution is determined by the results of these programs and by the new scientific results that become available. S. -P. Weng 40

A Successful Case of the Adaptive Approach l 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. l This decision was made before clear evidence that CFCs are harmful to the ozone layer. l The regulations were agreed in subject to periodic reviews to accommodate new scientific results. S. -P. Weng 41

Explosive Growth Events l 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 S. -P. Weng 42

Global Change – An Explosive Growth Event ? Exponential Growth Global Warming (from Philander’s “Is The Temperature Rising? ”) S. -P. Weng 43

Consequence of Late Response l 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 S. -P. Weng 44

Sooner Is Better Than Later l Is our global warming problem close to Day 1 or Day 100? (This is a scientific problem) l 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. l S. -P. Weng It is wiser to act sooner than later. 45

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. S. -P. Weng 46

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 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” thermohaline circulation.

What are the chances of thermohaline circulation shutting down? We don’t yet know the probability of 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.