Chapter 22. Chapter 22: Climate Change

What is the evidence that climate change is currently occurring...?

Why You Should Care

Historical climate records since 1850 show a strong trend of increasing temperature, but more importantly, the warming years are coming in groups and the overall trend is increasing. The climatic averages show a trend, but the effects are not uniform (polar areas are warming faster than tropical areas) and not increasing every year (there are still cold years, but recent decades are much warmer than 100 years ago). This warming is the most obvious with ice: Ice on land and on the oceans is thinning, breaking up, and shrinking.

Measuring current ice pack and current temperatures only gives us a snapshot. To go back and find data from before scientific measurements requires some clever technology. Gases from the atmosphere can be trapped as ice forms, mud freezes, or sediment is laid down. Temperature can be inferred from the presence and growth of ancient coral reefs, buried pollen grains, and tree rings.

Once past temperature and gas levels are collected, a computer model can be created that takes historic and current data and estimates the climate that fits that data. Models are never as accurate as real data, but they are the only technique available today to make hypotheses about past and future climate.

1.

Which of the following patterns of global temperature is CORRECT?

A.

Release of aerosols from air pollution sped up warming.

B.

Some areas of the world warmed much more than others.

C.

The first half of the 20th century was warmer than the historic average.

D.

There is a pattern of continuously increasing temperature over the past 120 years.

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2.

Which predicted effects of warmer global temperatures have been recorded on the Earth?

A.

Higher average temperatures

B.

More glacial ice melt

C.

Sea level rise

D.

All of the above

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3.

What patterns of precipitation has recent warming NOT caused?

A.

Increased number of drier than average events

B.

Increased number of hurricanes

C.

Increased number of wetter than average events

D.

Increased storm intensity

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4.

Why does the loss of ice show an inverse trend compared to sea levels?

A.

Thicker ice makes sea levels higher because ice floats.

B.

Higher sea levels come from smaller icebergs.

C.

Ice melts and becomes water that flows into the sea and raises sea level.

D.

Sea level is more dependent on water temperature.

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5.

Why does the map of the temperature anomalies for 2011 not show the same temperature for the whole world (or even for a whole continent)?

While the global temperature has been increasing, it is important to remember that this is climate, and weather still depends on local factors. Looking at Asia, there are warmer areas in the west and in the East and a large patch of cooler temperatures in the middle. Mountains, prevailing winds, and plant cover all modify weather and can warm or cool the air. The overall pattern globally is for warming.

6.

What have scientists NOT discovered from ice cores?

A.

Carbon dioxide levels and temperature are correlated over hundreds of thousands of years.

B.

Ice traps bubbles of air from past times that scientists can measure today.

C.

Ice cores do not have layers marking each year like tree rings do.

D.

All of the above have been discovered from ice cores.

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7.

Why do carbon dioxide levels vary by season (within a year)?

A.

Carbon dioxide levels fall during summer as plants photosynthesize.

B.

Carbon dioxide levels increase during winter as plants slow photosynthesis.

C.

Temperature increases during summer slow carbon dioxide release.

D.

Both a and b are correct.

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8.

Why does the slope of the CO₂ graph increase so steeply after 1950?

A.

Fossil fuel emissions increased rapidly with industrialization.

B.

Ice cores formed faster and stored more bubbles that were easier to measure.

C.

Melting polar ice caps released more carbon dioxide.

D.

None of the above

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9.

Why do the Vostok ice core data show that CO₂ and temperature move together, but not exactly at the same rate?

Carbon dioxide is just one of the forcers for the greenhouse effect—albedo, aerosol concentrations, and the Milankovitch cycles all modify the temperature, too. But in general, carbon dioxide and temperature change at about the same pace and with the same trend. This relationship is strong enough that the IPCC uses these data as a baseline for climate models.

10.

To match recent data better, climate models had to include which of the following?

A.

Anthropogenic factors

B.

Natural factors

C.

Older ice core data from Vostok

D.

Both a and b are correct.

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11.

Why do climate models with only natural factors have temperatures below observed temperatures?

A.

Anthropogenic factors increased the temperature to match observed temperatures.

B.

Higher temperatures were not possible with climate models.

C.

Natural factors were too great and overshot the observed temperatures.

D.

Small changes in the real world made it hard to match temperatures exactly.

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12.

Why do observed temperatures NOT exactly match the model's computed temperatures?

Climate is very complex, and small changes in emissions, albedo, and land use for the real world could have enough effect that computer climate models would not be able to match that level of detail.

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