2. Outline
• Introduction to climate change
• What changes climate?
• How do we know?
• Why should we care?
• What next—what can we do?
2
3. Climate Change-Definition
• Any change in climate over time, whether
due to natural variability or as a result of
human activity (IPCC)
• Change of climate that is attributed directly
or indirectly to human activity that alters
the composition of the global atmosphere
and that is in addition to natural variability
observed over comparable time periods
(UNFCCC)
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5. What changes climate?
Contd…
• Sun’s output
Energy output increased about 0.1% from 1750 to
1950, increasing temperatures by 0.1⁰C in the first
part of 20th century. But since 1979, when we began
taking measurements from space, the data show no
long-term change in total solar energy, even though
earth has been warming.
• Earth’s orbit
Repetitive cycles in Earth’s orbit that occur over tens of
thousands of years can influence the angle and
timing of sunlight. 5
6. • Drifting continents
In the distant past, drifting continents make a big difference
in climate over millions of years by changing ice caps at
the poles and by altering oceans currents, which transport
heat and cold throughout the ocean depths.
• Volcanic eruptions
Huge volcanic eruptions can cool earth by injecting ash and
tiny particles into the stratosphere.
• Greenhouse gases
Changes in the concentration of greenhouse gases, which
occur both naturally and as a result of human activities.
6
9. How do we know?
Scientists learn about the past climate from such things as
tree ring analysis, fossil evidence and analysis of patterns
and chemical composition in coral skeletons and ice cores.9
11. Computer models
Computer model used to forecast weather, climate models
simulate the climate system with 3-dimensional gird. It
performs trillions of calculations that describe changes in
many climate factors in the grid. 11
12. Why should we care?
Model correctly identify that the warming is due to man’s
activities, and that projections of future warming are
realistic. 12
13. Effects: Snow and ice
Grinnell Glacier, Glacier National Park
1900 and 2008
In Glacier National Park, there were 150 glaciers in 1850.
Today, there are 26. 13
17. Effects on precipitation contd…
• More water vapor held by a warmer atmosphere
also lead to heavier rains and more snowfall.
• But as storm tracks shift, it can also mean some
areas get drier.
• A 2004 study by the National Center for
Atmospheric Research found that the percentage of
Earth’s land experiencing serious drought had more
than doubled since the 1970’s.
17
18. U.K.: Train rails buckle
Germany: Lowest river levels
this century
France: >14,000
deaths Switzerland: Melting
glaciers, avalanches
Portugal: Forest fires
2003 European Heat Wave
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20. Impacts
AGRICULTURE WATER RESOURCES FORESTS
•Changes in forest composition and
•Shift in food growing areas •Change in water supply
•Changes in crop yields locations
•Decreases water quality •Disappearance of some forests
•High irrigation demand •Increased drought •Increased fires from drying
•Increased pest, crop •Increased flooding •Loss of wildlife habitat and species
diseases & weeds in warm
areas
BIODIVERSITY SEA LEVEL
•Extinction of some plant •Rising sea levels
•Flooding of low lying islands and
and animal species
•Loss of habitat coastal cities
•Disruption of aquatic life
WEATHER EXTREMES HUMAN POPULATION
vHUMAN HEALTH
•Increased death from heat and diseases
•Prolonged heat waves and •Increased deaths •Disruption of food & water supplies
drought •Spread of tropical disease to temperate areas
•More environmental
•Increased flooding •Increased respiratory diseases
refugees
•More intense hurricanes, •Increased water pollution from coastal flooding
•Increased migration
typhoons, tornadoes & violent 20
storms
21. Future Scenario
More CO₂ means a warmer
atmosphere.
Global mean temperatures in
some regions would be 8⁰C to
11⁰C warmer if CO₂ doubled
(top),
and 13⁰C if CO₂ quadrupled
(bottom).
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24. IPCC estimate sea level rise
( High emission scenario)
Thermal expansion of seawater ........ 28 cm
Glaciers and ice caps ......................... 12 cm
Mass balance .................................... - 3 cm
Increased flow ................................... + 3 cm
Total: 40 cm
Range of Estimates: 18-59 cm
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25. Future Scenario contd…
• Global average temperature are expected to
increase by about 1-7⁰C by the end of the century.
• Four major changes prior to sea level rise. They are:
Thermal expansion, mountain glacier melting,
Greenland ice and Antarctic ice sheet melting.
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26. What next—what can we do?
• Reducing our greenhouse gas emissions and our use
of fuels will not be easy, but it double. 26
28. 8 technologies that could avoid
8 wedges
•Produce more fuel-efficient vehicles
•Reduce vehicle use
•Improve energy-efficiency in buildings
•Develop carbon capture and storage processes
•Triple nuclear power
•Increase solar power
•Decrease deforestation/plant forests
•Improve soil carbon management strategies
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29. Individual actions
Plant
trees
Awareness
Use mass
programs
transit,
bicycle,
walk, roller
skate insulate, and
replace old
Buy water-saving windows
appliances and Buy products
toilets; installing with a U.S. EPA
low-flow shower Energy Star
heads. label
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Scientists have a good understanding of what has changed earth’s climate in the past: Incoming solar radiation is the main climate driver. Its energy output increased about 0.1% from 1750 to 1950, increasing temperatures by 0.2°F (0.1°C) in the first part of the 20 th century. But since 1979, when we began taking measurements from space, the data show no long-term change in total solar energy, even though Earth has been warming. Repetitive cycles in Earth’s orbit that occur over tens of thousands of years can influence the angle and timing of sunlight. In the distant past, drifting continents make a big difference in climate over millions of years by changing ice caps at the poles and by altering ocean currents, which transport heat and cold throughout the ocean depths. Huge volcanic eruptions can cool Earth by injecting ash and tiny particles into the stratosphere. Changes in the concentration of greenhouse gases, which occur both naturally and as a result of human activities, also influence Earth’s climate.
[Image 1] Earth’s surface absorbs heat from the sun and then re-radiates it back into the atmosphere and to space. [click, Image 2] Much of this heat is absorbed by greenhouse gases, which then send the heat back to the surface, to other greenhouse gas molecules, or out to space. Though only 1% of atmospheric gases are greenhouse gases, they are extremely powerful heat trappers. By burning fossil fuels faster and faster, humans are effectively piling on more blankets, heating the planet so much and so quickly that it’s hard for Mother Nature and human societies to adapt.
While there are many substances that act as greenhouse gases, two of the most important are water and carbon dioxide, or CO2.
We know about the present changes from observations taken at the surface and in the atmosphere. One of the questions often asked is if the warming isn’t an artifact of urban heat islands or changes in how measurements are done. Scientists have looked at this extensively. For example, when a NASA group removed all but 200 true rural sites, the warming pattern persisted. a U.S. National Climatic Data Center study found no statistically significant urban heat island effect in 289 U.S. stations. And finally, even though there are no cities in the oceans, warming has been measured over them too.
[Image 1] More water vapor held by a warmer atmosphere also leads to heavier rains and more snowfall. Intense precipitation over the U.S. has increased 20% over the last century. [click, Image 2] But as storm tracks shift, it can also mean some areas get drier. A 2004 study by the National Center for Atmospheric Research found that the percentage of Earth’s land experiencing serious drought had more than doubled since the 1970s.
[Image 1] There will always be natural variability, and some places and some years will be warmer or cooler than average. In general, however, summers will get hotter, not only because of higher temperatures but also because humidities will increase. That means that heat waves, like the one that killed 35,000 people in Europe in 2003, will become more common. [click, Image 2] On the plus side, winters will be warmer in many places, reducing heating bills. And the number of days with frosts is likely to decrease.
[Image 1] The main tool for both past and present climate analyses are computer climate models. Much like the models used to forecast weather, climate models simulate the climate system with a 3-dimensional grid that extends through the land, ocean, and atmosphere. The grid may have 10 to 60 different levels in the atmosphere and surface grid spacings of about 60 by 90 miles (100 by 150 km)—the size of Connecticut. The models perform trillions of calculations that describe changes in many climate factors in the grid. [click, Image 2] The models project possible climates based on scenarios that cover a range of assumptions about global population, greenhouse gas emissions, technologies, fuel sources, etc. The model results provide a range of possible impacts based on these assumptions.
[Image 1] A common critique of climate predictions is, “If weather model forecasts aren’t reliable more than a week out, how can models predict climate decades in the future?” While weather and climate models are based on similar physics, they are not predicting the same thing. Weather forecasts look at the day-to-day changes on a local level, and subtle chaotic atmospheric variations make short-term weather forecasts difficult beyond 8-10 days. [click, Image 2] Climate predictions are focused on longer-term influences of the sun, oceans, land, and ice on the atmosphere. Instead of predicting a temperature at a particular place at a particular hour, climate modules project an average temperature over a year or longer in a large region or over the entire globe.
[Image 1] This triangle can be divided into 8 wedges representing one billion tons each.
Here are examples of 8 technologies that could save 8 billion tons, or 8 wedges, of carbon. Some of these we could do right away, while others are based on technologies still being studied, such as capturing and storing carbon. [Details on strategies: Efficient vehicles: Double car fuel efficiency in 2055 from 30 miles per gallon (mpg) to 60 mpg Reduced vehicle use: Halve the miles traveled by the world’s cars in 2055 Efficient buildings: Cut emissions by 25% in all buildings CCS electricity: Capture and store carbon from 800 large coal power plants or 1600 large natural gas power plants Triple the world’s current nuclear capacity Solar electricity: Increase solar capacity 700 times Forest storage: Halve global deforestation and double forest planting in 50 years Soil storage: Apply carbon management strategies to all of the world’s farm fields] This list represents only some of the possible strategies, but choosing strategies will not be easy. However, the longer we wait to reduce emissions, the higher the target will need to be, and the more adaptation will be necessary. In 2004, when the wedges concept was first introduced, the target was only 7 billion tons.
As you can see, there are many ways society can approach the struggle to reduce carbon emissions, but there is no single solution. Many of the strategies mentioned are the realm of governments. And the ever-growing world population means that we’ll have to work that much harder to reduce global emissions. But on an individual level, there are many things you can do to make a difference. [click to reveal examples] Lots of other ideas are available on the Internet.
As you can see, there are many ways society can approach the struggle to reduce carbon emissions, but there is no single solution. Many of the strategies mentioned are the realm of governments. And the ever-growing world population means that we’ll have to work that much harder to reduce global emissions. But on an individual level, there are many things you can do to make a difference. [click to reveal examples] Lots of other ideas are available on the Internet.
As you can see, there are many ways society can approach the struggle to reduce carbon emissions, but there is no single solution. Many of the strategies mentioned are the realm of governments. And the ever-growing world population means that we’ll have to work that much harder to reduce global emissions. But on an individual level, there are many things you can do to make a difference. [click to reveal examples] Lots of other ideas are available on the Internet.
