Atmosphere& Climate Change

Section #3:Global Warming

Greenhouse Effect• sun’s energy

streams into the car windows

• carpets & upholstery absorb the light energy & change it into heat energy

• heat energy cannot pass back out the windows as easily as light energy can

• heat gets trapped inside & continues to build up

The Earth as a Greenhouse

• Earth is similar to a greenhouse• atmosphere acts like the glass

allowing sunlight to enter & heat the Earth’s surface

• heat radiates back from the Earth, some escapes into space, some is absorbed by gases in the troposphere - warming the air

What do we call this process?

•the process of heat absorption is called the . . .

GREENHOUSE EFFECT

Greenhouse Gases

• gases that absorb & radiate heat• major greenhouse gases

– water vapor *– carbon dioxide *– chlorofluorocarbons– methane– nitrous oxide

How the Greenhouse Works

Measuring CO2 in the Atmosphere

• geochemist Charles Keeling installed an instrument at the top of a tall tower on Mauna Loa in Hawaii in 1958

• he could precisely measure CO2 in the air far away from forests & cities

Why did he need to get away from cities & forests?

• in a forest, CO2 levels rise & fall with the daily rhythms of photosynthesis

• near cities, CO2 from traffic & industrial pollution raises the local concentration of the gas

• steady winds that have come thousands of miles over the Pacific Ocean blow over Mauna Loa, far from the affects of forests or cities

Carbon Dioxide Levels

• Keeling believes that the air over Mauna Loa represents the average carbon dioxide levels for the entire Earth

• Keeling’s 1st measurement in 1958 was 314 parts per million

• over the next year, he noticed that the levels rose & fell with the seasons

Seasonal Changes

• summer levels = lower• WHY?

– growing plants use more CO2 for photosynthesis than they release in respiration

• winter levels = higher• WHY?

– dying grasses & fallen leaves decay & release the carbon that was stored in them

Rising CO2 Levels

• after a few years of measurements, Keeling noticed a change beyond the seasonal fluctuations

• each successive year, the carbon dioxide levels in the winter were higher than the previous year

• also each year, the summer levels did not fall as low

Graph Showing Overall Increase + Seasonal

Fluctuations

Where do we stand now?

• the graph shows CO2 levels from 1958 to 2000

• in those 42 years, carbon dioxide has gone from 314 ppm to 368 ppm, an increase of 54 ppm (or 17%)

• scientists hypothesize that this increase is due to the burning of fossil fules

Earth’s Temperature

• scientists also think that because greenhouse gases trap heat near Earth’s surface, more greenhouse gases in the atmosphere will result in an increase in global temperatures

• supporting data for this view comes from a comparison of CO2 levels in the atmosphere & average global temperatures for the past 400,000 years

Where is the CO2 Coming From?

• power plants that burn coal or oil • cars that burn gasoline• the millions of trees that are

burned to clear tropical rain forests for farming

• plus the release of other greenhouse gases

Where Are the Gases Coming From?

How Certain is Global Warming?

• a predicted increase in global temperatures resulting in a warmer Earth is referred to as global warming

• many scientists believe that the warming trend will continue throughout the 21st century

Global Surface Temperatures

How Certain is Global Warming?

• some scientists disagree that the warming trend is due to an increase in greenhouse gases

• these scientists believe that the warming is part of natural climatic variability pointing out that data reflects widespread fluctuations in temperature over geologic time

Modeling Global Warming

• unable to make accurate predictions

• climatic patters are complex & too many variables must be taken into account to be solved even using today’s fastest computers

• models have evolved quickly as more data is collected & analyzed, & as faster computers are built

Modeling Global Warming

• Variables to take into account when making predictions:– carbon dioxide levels– prevailing winds– ocean circulation patterns– temperature– rainfall patterns– sea level fluctuations– cloud coverage– amount of water vapor in atmosphere– amount of ice– changes in vegetation– ocean chemistry

Maps developed by computer models: the left shows the effect of greenhouse gases before sulfur

pollution was added & the right one shows a cooling effect from the addition of sulfur pollution

Consequences of a Warmer Earth

• Over the past thousands & even millions of years, Earth’s climate has changed dramatically

• scientists are not sure how quickly the Earth will warm or how severe the effects of global warming might be

• the impacts could set into play a number of serious environmental problems including– disruption of global weather patterns global– rise in sea levels– adverse affects on human health,

agriculture, plant & animal populations

Melting Ice – Rising Sea Levels

• rising temps will cause a decrease in the amount of ice and snow at the poles

• melting would cause sea levels to rise leading to the flooding of coastal wetlands & other low-lying areas

• people living near coasts would loose their homes & businesses

• beaches could be eroded• salinity in bays & estuaries could

increase which could impact fish reproduction

• could flood fresh water aquifers near coasts

A 11,000 km2 iceberg that split from the Ross Ice Shelf in Antarctica in March 2000

Global Weather Patterns

• as temps rise, the oceans will absorb more heat, leading to an increase in the # of hurricanes or typhoons

• could shut down or change ocean circulation patterns which would then impact the world’s weather

• this would lead to more rainfall in some areas (flooding) & less in other areas (droughts)

Human Health Problems

• increase in heat-related deaths – especially in the elderly & young who are more susceptible to heat exhaustion

• increases in ground-level ozone which could lead to higher temps that could impact those with respiratory illnesses

• increase in insects & the diseases they spread (note – malaria & encephalitis from mosquitoes)

Agriculture

•increases in temps might lead to–droughts–decrease in crop yields – not enough food for humans & other animals

– increase need for irrigation that might deplete freshwater stores (aquifers)

Field of Drought

Effect on Plants & Animals

• increases in temps might lead to–changing the types of plants that can grow in an area which will impact the local food chain

–some areas will not have enough moisture to grow much of anything

–ocean food chains could be impacted by a decrease in plankton

–destruction of coral reefs

Recent Findings

•IPCC (Intergovernmental Panel on Climate Change) – network of the world’s leading climatologists from 70 countries

•issued TAR (Third Assessment Report) in 2001 which describes the current knowledge about the global climate system & gives estimates of the future

Recent Findings

•the average global surface temperature increased by 0.6°C during the 20th century

•snow & ice coverage have decreased

•average global sea levels have risen

•concentrations of greenhouse gases have continued to increase

Reducing the Risk

•in 1997, reps from 160 countries around the world set timetables for reducing greenhouse gas emissions

•when 55% of the attending nations ratify this treaty called the Kyoto Protocol these timetables will go into effect

Kyoto Protocol

•requires developed countries to decrease emissions of CO2 & other greenhouse gases by an average of 5% below their 1990 levels by the year 2012

•the U.S. decided not to ratify the treaty in 2001 although most developed countries have

What We’re Doing Now:

•recognizing the existence of global warming

•recognizing the human impacts•reforestation projects to reduce

CO2

•reducing car exhaust emissions

Reforestation projects (like

this one in Haiti) may

help to offset a portion of

CO2 emissions because

plants take in CO2 during photosynthes

is.

Problems:

•different countries are facing problems in the following factors and this is leading to conflicts between developed & developing countries–economic factors–political factors–social factors

Developing countries are projected to make up half of all CO2 emissions by

2035