VIDEO
What the Data Are Telling Us
When the IPCC released its previous report (AR3) in 2001, much of the discussion at the time in the media and various publications referred to “the debate on global warming.” Although there remain open issues and ongoing investigations, a broader consensus is now emerging.
The IPCC presented the following conclusions in its 2007 report (AR4):
• Warming of the climate system is “unequivocal.”
• There is a “very high confidence” that human activities since 1750 have contributed to this net warming of the earth.
• The increase in the concentration of carbon dioxide in the atmosphere is the single most important factor driving the increase in global temperatures.
• If tomorrow, carbon dioxide emissions into the atmosphere were to stop completely, carbon dioxide levels already in the atmosphere will cause an average sea level rise of about 1.4 meters (4.6 feet).
• By as early as 2030, 75 million to 250 million people in Africa will suffer water shortages.
• Residents of many of Asia’s large urban areas will be at great risk from river and coastal flooding.
• Extensive loss of the species is expected especially in Europe.
• In North America, longer and hotter heat waves and greater competition for water resources are forecast.
What Is the IPCC?
Much of the climate modeling is developed, reviewed, and reported by the IPCC.
• The IPCC was established by member countries of the United Nations in 1988.
• Its function is to assess scientific data relating to climate change.
Over 2,500 scientists from around the world contribute to the IPCC’s assessment efforts.
• The IPCC published overall assessments in 1990, 1995, 2001, and 2007.
• Three separate working groups were set up to focus on the physical science of climate change, the impact on people and nature, and methods to correct the problem.
• The results of the study groups are peer reviewed by hundreds of reviewers from over 130 countries.
• In 2007 the IPCC along with Al Gore won the Nobel Peace Prize for their work on climate change.
Cause and Effect
Temperature measurements from around the world indicate that the temperature of the earth is increasing in a way that is unprecedented in recent times. What is causing this to happen? How much is natural, and how much is the result of human activity? Will it be a big deal? Will it be catastrophic? Is there anything we can do to reverse the course that has apparently been set in motion? These questions will be addressed in the sections of this book that follow.
Key Ideas
• Reliable direct temperature measurements of the earth’s air temperature have been made for roughly the past 150 years. This is known as the instrumental record.
• Direct measurements show that the average global temperature has increased by 0.74°C (1.3°F) during the past 100 years. At present, the temperature is increasing at a rate of 0.177°C (0.211°F) every 10 years.
• The average global temperature of the earth is now 14.4°C (57.9°F). One hundred years ago, the average global temperature was 13.7°C (56.5°F).
• Eleven of the past 12 years were the hottest on record.
• To compare present-day temperatures with temperatures during historical periods, scientists use indirect (or proxy) methods to determine temperatures in the past.
• Proxy methods include ice cores, tree rings, coral layers, ocean sediment, and boreholes.
• The northern hemisphere is warming faster than the southern hemisphere.
• The heat island effect causes locally higher temperatures but is not mistaken for and is not a cause of global warming.
• Satellites have determined that the troposphere is warming slightly more rapidly than at the surface, which is consistent with the concept of greenhouse gas absorption of heat.
Review Questions
1. What is meant by a temperature anomaly?
(a) Temperature extremes
(b) A sudden change in a temperature
(c) The amount that a temperature reading varies from an established baseline
(d) An error in a temperature reading
2. Approximately how much did the average global temperature increase over the past 100 years?
(a) 0.25°C (0.5°F)
(b) 0.75°C (1.4°F)
(c) 2.0°C (3.6°F)
(d) 5.0°C (9.0°F)
3. Which of these is a proxy method of characterizing temperature?
(a) Coral-core layer analysis
(b) Weather station at Big Sky Airport in Phoenix
(c) Air measurements outside of Anchorage, Alaska
(d) Rough estimates of air temperature using an uncalibrated thermometer
4. How does the greater atomic mass of oxygen-18 make it useful in determining prehistoric temperatures in ice-core samples?
(a) Oxygen-16 changes into oxygen-18 at higher temperatures.
(b) Oxygen-18 is released from water molecules at higher temperatures.
(c) Oxygen-18 is slightly heavier and is incorporated more into an ice layer during warm weather.
(d) Water with oxygen-18 freezes at a lower temperature than water with oxygen-16.
5. What is the primary function of the IPCC?
(a) To collect temperature data
(b) To perform measurements on ice cores
(c) To perform research on ways to reduce greenhouse gas emissions
(d) To analyze data
6. How does the temperature change over land areas compared with the change of ocean temperature?
(a) Lower
(b) Higher
(c) Same
(d) Mixed bag
7. According to GISP2 ice-core data, about how much warmer were previous interglacial warm periods (when ice caps had melted) than today?
(a) 0.75°C (1.4°F)
(b) 1.5°C (3.6°F)
(c) 5.0°C (9.0°F)
(d) 10.0°C (2.7°F)
8. Where is the atmospheric temperature increasing most rapidly?
(a) Alaska
(b) The equator
(c) The Pacific Ocean
(d) Northern Europe
9. How are satellites able to measure the temperature of the atmosphere?
(a) By measuring how much light is reflected from clouds
(b) By measuring invisible electromagnetic energy radiated from the earth
(c) By sending a microwave signal and measuring how much is reflected back
(d) By observing the movement of clouds and ocean currents
10. How are temperatures changing vertically in the atmosphere?
(a) Both the troposphere and the stratosphere are warming.
(b) Both the troposphere and the stratosphere are cooling.
(c) The troposphere is cooling and the stratosphere is warming.
(d) The troposphere is warming and the stratosphere is cooling.
