Chapter 6: Climate Change

According to the 4th Assessment Report of the IPCC, global temperature is predicted to rise by how many degrees centigrade in the 21st century?

1 to 4 Feedback: Of course, it is more important to know what impacts may be expected from this range of temperature increase. Even impacts from the lower end of the range will be severe.

Until about 1950, levels of atmospheric CO2 had not exceeded what concentration over the previous 800,000 years?

300 ppm (parts per million) Feedback: It's important to understand that abundances alone are not significant without knowing what compound is involved. For example, we are also concerned about the abundance of methane in the atmosphere, even though it is 3 orders of magnitude less than the abundance of carbon dioxide.

Today, the atmospheric concentration of CO2 is over

400 ppm

At the current rate of melting of the Antarctic ice cap, sea level is expected to rise by at least how much by 2100?

About 1 meter Feedback: Although this estimate is a moving target, the most recent projections are for 1-2 meters of sea level rise by 2100 from Antarctic ice.

Ocean Acidification is caused by the increase in which of the following atmospheric gases?

Carbon Dioxide Feedback: CO2 reacts with water to increase its acidity (free hydrogen ions). Acid water causes the breakdown of calcite, the mineral from which many forms of marine life create their skeletons or shells.

The variation between glacial and interglacial (warm) climate in the last 800,000 years may best be explained by

Cyclical changes in the Earth's position with reference to the Sun Feedback: The astronomical cycles observed by Milankovich and the predictions he made regarding historic climate change based on those observations have led to the generally accepted idea that Earth's position in relation to the Sun produces natural variations in climate over tens to hundreds of thousands of years.

The easiest way for most U.S. residents to reduce their carbon emissions would be to

Eat less beef. Feedback: Just changing from average meat consumption to a beefless diet would reduce annual carbon emissions associated with a single person's diet by 25%.

T/F: A 1 meter rise in sea level will not have much impact on life in the united states...

False Feedback: Yes, there will be a big impact on the U.S. See slide 32 showing the change in the amount of dry land in the Miami, FL, region.

Global warming is producing more prolonged and frequent heavy rainfall events in part because

Higher temperatures increase the ability of air to hold water vapor feedback: The warmer the air, the more water vapor it can hold per unit of mass. This means that on average, global warming works to make the atmosphere like an ever-growing sponge which has much more water to release when local cooling causes precipitation.

According to your lecture on climate change, the "smoking gun" that demonstrates the anthropogenic cause for current global warming is

Increased ratio of light to heavy carbon in the atmosphere. Feedback: Fossil fuels come from the buried remains of plants and phytoplankton, hence are enriched in carbon 12 because these organisms preferentially incorporate light carbon into their bodies during photosynthesis. Release of this light carbon when those fuels are burned has produced a steady increase in the amount of 12C vs. 13C in atmospheric CO2.

The very rapid rise in atmospheric concentration of CO2 since the 1950's is primarily attributable to...

Increases in the rate of global population growth. Feedback: increased use of fossil fuel, primarily for energy production, is associated with rapid population growth since 1950. See pp. 246-247 in your text, slide 36 in the powerpoint.

The decreased area of summer ice cover in the arctic has what impact on climate?

It reduces planetary albedo Feedback:Ice is more reflective than sea water, so significant decrease in planetary ice, whether floating on the ocean or resting on land, causes the planet to be less reflective overall. Thus melting of sea ice creates a positive feedback loop, increasing global warming.

Compound to the average global temperature over the last 4.5 Gy, our climate today is

Moderately Colder Feedback: Given all the talk about global warming, you would want to say that Earth is much warmer now than in the geological past, but slide 17 demonstrates that we are just coming out of a glacial period and are still a little bit colder than the 4.5 Gy average.

Thawing of permafrost provides what kind of feedback to global warming?

Positive Feedback: A positive feedback works in the same direction as the initial change to a system. Global warming is the initial change, melting permafrost is one of the effects of the change and melting permafrost releases more greenhouse gases into the atmosphere, reinforcing global warming.

Climate scientists use computer models to predict climate in the future. The reliability of climate models is primarily determined by

Running the model with known past starting conditions and comparing its output with observers. Feedback: If a model can reproduce observations from the past given known starting conditions, then it is reasonable to assume that its predictions about the future will be more or less reliable.

The relationship between temperature and isotopic character of snow or rain at a given latitude is

The higher the temperature, the heavier the isotopic character of precipitation Feedback: empirical (observational) relationship between heavy snow during the Antarctic summer and light snow during the Antarctic winter. So higher temperature is associated with heavier snow (or rain) at a given latitude.

On the time scale of thousands of years, the oxygen isotopic character of the ocean bears what relationship to global average temperature?

The lower the temperature, the heavier the isotopic character of the ocean. Feedback: interglacial periods (global warm periods) do not sequester light isotopes in ice, so the ocean is isotopically lighter than during glacial (global cold) periods.

Over the last 100 years or so, the number of wildfires reported annually in California has nearly

Tripled Feedback: Gone from 100 to about 275 or nearly tripled.

What is the difference between weather and climate?

Weather studies atmospheric events over short time scales; climate studies the same events over long time scales. Feedback: The accumulation and analysis of data about atmospheric and related phenomena (e.g. ocean temperature) over a multi-decadal time scale and making projections for the future over the same time scale is the object of climate science.

Which of the following gases has the greatest impact on the greenhouse effect? a. Carbon Dioxide b. Methane c. Nitrous Oxide d. Hydrochlorofluorocarbon

a. Carbon Dioxide feedback:The model experiment of Lacis et al. 2010 (slide 8) showed that CO2 is a principal control on Earth's climate and therefore on the abundance of water vapor, the greenhouse gas with the broadest range of radiative absorption.