1. Are global temperatures rising?
Coin toss. The U.N.'s weather agency reports that the past decade was the warmest on record since reliable measurements began, and temperatures have been on the rise since about 1977. But those warm temperatures have remained flat — and steep — for a decade since a spike in 1998 that coincided with the weather pattern El Nino.
3. Is climate change man-made?
Coin toss. Temperatures have seen a global rise in the past 30 years, following a trend of increasing carbon dioxide emissions worldwide which trap heat and raise temperatures. But the Earth has also undergone periods of temperature stagnation and cooling since 1880, even as industrialization has led to growing emissions. Many climate scientists attribute warming to man-made pollution and deforestation, while others argue that temperatures are changing because of natural climatic and solar cycles.
4. Are sea levels rising?
Yes. Sea levels have been rising at a rate of about 3.3 mm a year since 1993, when satellite altimeters began tracking the data. Tidal gauging records, which vary from region to region, indicate a steady rise in sea levels of about 1.7 mm a year since 1870, which fits in with an overall trend stretching back over 200 years.
5. Are global sea levels rising because of melting glaciers and ice sheets?
Coin toss. Tides, wave erosion, and storm systems create temporary changes in sea levels; sea levels also shift seasonally and because of weather events like El Nino; and rising temperatures in the sea have caused waters to expand. But many scientists hold that melting glaciers and ice sheets are contributing up to a third of the rise in sea levels.
6. Is CO2 a pollutant?
No. Carbon dioxide is a naturally occurring chemical that makes up about .04 percent of the Earth's atmosphere. The EPA has labeled CO2 a danger to human health, highlighting the risk of industrial emissions, but the gas also plays a vital role in the Earth's carbon cycle and is used by plants in photosynthesis.
7. Is the ice cap at the North Pole shrinking?
Yes. The Arctic polar ice cap has been in overall decline since NASA satellites began recording data in the late 1970s. The overall rate of decline is about 4.5 percent of the overall mass in a decade. Though ice levels hit record lows in 2005, there has been a slight rebound in recent years that scientists believe is unlikely to hold.
8. Is the ice cap at the South Pole shrinking?
Coin toss. Recent data compiled from NASA measurements suggest a loss of ice in the Antarctic, but those results come from a satellite that measures changes in gravity and doesn't track the amount of ice itself. Direct measurements show a notable increase over the past 30 years. The overall extent of Antarctic sea ice has "increased at a rate of 100,000 square kilometers a decade" since the 1970s, according to the British Antarctic Survey, though nine ice shelves have collapsed and GPS measurements indicate declining ice in the western Antarctic.
9. Is the hole in the ozone layer growing?
No. The Earth's natural sunscreen, a layer of ultraviolet-reflecting ozone in the stratosphere, has been heavily depleted in the area above Antarctica. But the damage appears to be neutralized as the size of the "hole" itself has stabilized and the amount of ozone has stopped falling. Scientists hope that a 1989 ban on chemicals that were depleting the ozone layer will lead to a recovery by 2040.
10. Is global warming eating away the snows of Kilimanjaro?
Coin toss. The glaciers at Tanzania's highest peak have been shrinking for a century, well before global temperatures increased. While some climate scientists say rising temperatures and deforestation are melting the famous glaciers of Mt. Kilimanjaro, others argue that solar radiation is sublimating the ice — turning it directly to gas.
11. Does climate change affect animals?
Yes.Rising temperatures have sent many animals seeking higher elevations and cooler climes. Birds are migrating at different times of the year, and periods of hibernation have shifted with the weather. Some scientists speculate that the Golden Toad of Africa even went extinct because of increased temperatures.
12. How many endangered animal species are there?
8,216. There are more than 8,000 endangered species worldwide and another 9,075 threatened species, according to the International Union for Conservation of Nature. Endangered species are in danger of going extinct; threatenedspecies are those likely to become endangered in the foreseeable future. There are 613 animal species listed as threatened or endangered in the U.S. alone.