CLIMATE: Climate Change Anthropogenic (HW 5 Questions/Review)

Global temperatures are forecast to rise about 3°C by the year 2100. Which parts of the world are expected to experience the greatest temperature rise?

Arctic

Which of the conditions below would most likely produce warming at the earth's surface?

Increase the amount of high-level global cloud cover

The most recent warming trend experienced over the Northern Hemisphere could be the result of:

Increasing levels of greenhouse gases (i.e. anthropogenic levels of CO2)

Which of the following is a positive feedback on climate

Increasing warming melts polar sea ice which causes surface to have lower albedo

If the earth had no greenhouse effect, would the earth's average surface temperature be higher or lower than it is presently? Explain.

It would be lower because heat would leave the atmosphere through infrared radiation. The outpouring of solar energy constantly bathes the earth with radiation while the earth, in turn, constantly emits infrared radiation. If we assume that there is no other method of transferring heat then, when the rate of absorption of solar radiation equals the rate of emission of infrared earth radiation, a state of radiative equilibrium is achieved. The average temperature at which this occurs is called the radiative equilibrium temperature. At this temperature, the earth (behaving as a blackbody) is absorbing solar radiation and emitting infrared radiation at equal rates, and its average temperature does not change. As the earth is about 150 million km (93 million mi) from the sun, the earth's radiative equilibrium temperature is about 255 K (0°F, -18°C).

Climate models predict that if average global temperatures rise by about 3°C, average global precipitation will:

Lead to more precipitation. More water vapor in the atmosphere will lead to more precipitation. According to models, global average precipitation will most likely increase by about 3-5% with a minimum increase of at least 1% and a maximum increase of about 8%. Yet, changes in precipitation will not be evenly distributed. Some locations will get more snow, others will see less rain. Some places will have wetter winters and drier summers.

How does a positive feedback mechanism differ from a negative feedback mechanism? Is the water vapor-greenhouse feedback considered positive or negative? Explain.

A positive feedback mechanism is a process which is reinforced by other processes. A negative feedback mechanism is a process which is weakened by interactions among other variables. The water vapor-temperature increase process is a positive feedback mechanism. As temerpatures rise it could lead to more water vapor in the atmosphere, which in turn is a greenhouse gas. In this respect it is a positive feedback. If, on the other hand, the water vapor produces more thibk clouds this could block out sunlight and be a negative feedback mechanism. Current thinking is water vapor is more a positive feedback than negative.

How much has the global temperature risen since 1880?

According to an ongoing temperature analysis conducted by scientists at NASA's Goddard Institute for Space Studies (GISS), the average global temperature on Earth has increased by about 0.8° Celsius (1.4° Fahrenheit) since 1880.

Everything else being equal, a gradual increase in global CO2 would most likely bring about:

An increase in surface air temperature

Why do climate scientists now believe that most of the warming experienced during the last 50 years was due to increasing levels of greenhouse gases, and not natural causes?

Because evidence from climate models and past temperature histories support the idea that the recent warming is largely due to greenhouse gases. (Anthropomorphic CO2 is a prime example)

Sahel

Belt south of the Sahara where it transitions into savanna across central Africa. It means literally 'coastland' in Arabic. The Sahel (/səˈhɛl/) is the ecoclimatic and biogeographic zone of transition in Africa between the Sahara to the north and the Sudanian Savanna to the south. Having a semi-arid climate, it stretches across the south-central latitudes of Northern Africa between the Atlantic Ocean and the Red Sea.

Which below is not one of the possible consequences of global warming predicted by climate models?

Lowering of sea levels. The other options are all possible consequences of global warming: accumulations of additional snow in Antarctica, a reduction in average precipitation over certain areas, a cooling of the upper atmosphere, a drop in the rate of ozone destruction in the stratosphere

A biogeophysical feedback mechanism in the Sahel relates:

Reduced vegetation to a decrease in surface temperatures and a reduction in rainfall.

If the polar ice sheets in the Arctic Ocean all melt as expected this century how much will sea level rise?

Sea level will rise over 10 cm

Explain how the earth's atmospheric greenhouse effect works.

Water vapor and CO2 (and nitrous oxide, methane, and ozone) selectively emit radiation at infrared wavelengths. This radiation travels away from these gases in all directions. A portion of this energy is radiated toward the earth's surface and absorbed, thus heating the ground. The earth, in turn, radiates infrared energy upward, where it is absorbed by these gases, warming the lower atmosphere. In this way, the selectively-absorbing greenhouse gases absorb and radiate infrared energy and act as an insulating layer around the earth, keeping part of the earth's infrared radiation from escaping rapidly into space. Consequently, the earth's surface and the lower atmosphere are much warmer than they would be if these selectively absorbing gases were not present.

What are the most abundant selectively absorbing greenhouse gases in the earth's atmosphere?

Water vapor followed by carbon dioxide. The most abundant is water vapor, though it is variable. The second most abundant is carbon dioxide.

What are some of the important roles that water vapor plays in our atmosphere?

Water vapor is an extremely important gas in our atmosphere. Not only does it form into both liquid and solid cloud particles that grow in size and fall to earth as precipitation, but it also releases large amounts of heat - called latent heat - when it changes from vapor into liquid water or ice. Latent heat is an important source of atmospheric energy, especially for storms, such as thunderstorms and hurricanes. Moreover, water vapor is a potent greenhouse gas because it strongly absorbs a portion of the earth's outgoing radiant energy.

List the most abundant greenhouse gases in the earth's atmosphere. What makes them greenhouse gases?

Water vapor, carbon dioxide, methane, nitrous oxide, chlorofluorocarbons. They are greenhouse gases because they absorb a portion of the earth's outgoing infrared radiation and radiate it back to earth.