Global Warming Test: The Real Answers

This post is by Lisa Moore, Ph.D., a scientist in the Climate and Air program at Environmental Defense Fund.

There’s an email making the rounds lately – an invitation to take a Global Warming Test. It starts off reasonably enough (yes, global warming is real), but then quickly devolves into ridiculousness – ridiculousness presented in a way that looks misleadingly "scientific".

For those interested in truth, here are the real answers to the Global Warming Test.

1) "Global warming" is a real phenomenon: Earth’s temperature is increasing. (True/False)

Correct Answer: True

Today’s temperature is probably higher than it’s been in at least 1300 years – mostly due to human activities.

2) The "Greenhouse Effect" is real. (True/False)

Correct Answer: True

A background greenhouse effect is natural to the Earth. Without it, the Earth’s average temperature would be an uninhabitable 0°F. But human activities have increased the greenhouse effect, causing rapid global warming.

3) The main cause of Global Warming is:

a) pollution from factories and automobiles
b) orbital eccentricities of Earth and variations in the Sun’s output
c) the Greenhouse Effect

Correct Answer:  a) pollution from factories and automobiles, and c) the Greenhouse Effect

Today’s rapid global warming is caused by increased concentrations of greenhouse gases in the atmosphere. The additional greenhouse gases come from human activities such as industrial pollution and tropical deforestation. It is not caused by orbital eccentricities or variations in the Sun’s output.

4) The Greenhouse Effect is caused primarily by:

a) water vapor
b) carbon dioxide
c) ozone-destroying aerosol sprays

Correct Answer: b) carbon dioxide

Although water vapor traps more heat than carbon dioxide (CO₂), increasing greenhouse gases like CO₂, not water vapor, is what drives global warming. Air warmed by CO₂ holds more water vapor, enhancing the effect. To interrupt this vicious cycle and stop global warming, we must control the emission of greenhouse gases like CO₂.

5) Which most accurately describes the effects of Global Warming in the United States over the last 100 years?

a) temperatures have risen > 5° C
b) temperatures have risen > 2° C
c) temperatures have risen < 1° C

Correct Answer: c) temperatures have risen < 1° C

Global temperatures have increased by about 0.75°C over the past 100 years (see this chart from NASA). U.S. temperatures have risen by nearly the same amount.

It may sound like a small number, but the impacts on Earth systems and global climate are already dramatic. Scientists predict much more warming in the future unless we cut greenhouse gas emissions.

6) How much carbon dioxide (CO₂) is in Earth’s atmosphere today?

a) 10% or greater
b) 2% to 10%
c) less than 1/10th of 1%

Correct Answer: c) less than 1/10th of 1%

CO₂ is about 0.038 percent of the Earth’s atmosphere. This sounds insignificant, but even small concentrations of greenhouse gases can have a large effect.

Since the start of the industrial revolution, CO₂ levels have risen about 33 percent, and the level of methane (a more potent greenhouse gas) has more than doubled.

7) Carbon dioxide from coal-fired power plants damages forests. (True/False)

Correct Answer: True

Nearly 20 percent of global CO₂ emissions come from cutting down forests, which certainly counts as damage!

Rising levels of CO₂ from industrial emissions have a complex effect on forests and other plants. In the western U.S., warming and drying have encouraged widespread beetle outbreaks and increasing wildfires. Some plants respond to CO₂ by growing more rapidly, but scientists also have found that many crops grown in high CO₂ conditions have lower nutritional value.

8) Which answer below provides the best explanation for the following temperature record?

< graph of Medieval Warm Period and Little Ice Age temperatures, origin unknown >

a) Industrial pollution from factories, power plants, and cars caused global warming
b) Natural variations in global temperatures may occur in roughly 500-years cycles
c) Global cooling occurred as a result of the Renaissance Period

Correct Answer: N/A, data in graph not accurate

The actual temperature record is not depicted in this graph. The "Medieval Warm Period" wasn’t as warm as temperatures are today, and it may not have been a global phenomenon. Like the "Little Ice Age", it’s most prominent in records from Europe. Scientists think the cooler temperatures between the 14^th and 19^th centuries may have been caused by changes in solar energy and/or the Gulf Stream. But natural factors like these have not contributed much to today’s warming trend.

9) Which of the following is not true about an increasing greenhouse effect?

a) the consensus of scientists is that the problem warrants drastic action
b) nighttime temperatures may increase, but daytime temperatures will not
c) the coldest, driest regions of the planet will warm first

Correct Answer: b) nighttime temperatures may increase, but daytime temperatures will not, and c) the coldest, driest regions of the planet will warm first

Both daytime and nighttime temperatures are already increasing. Northern areas are warming more quickly, but global warming is evident around the world. Scientists are calling for prompt action to cut greenhouse gas emissions.

10) Which temperature measuring method most accurately measures global warming?

a) ground-based thermometers
b) orbiting weather satellites
c) weather balloons

Correct Answer: a) ground-based thermometers, and b) orbiting weather satellites

All of these measurement techniques are useful, and the results consistently show warming. Some people point to an old discrepancy in satellite records as evidence that global warming isn’t happening. But the discrepancy was resolved more than two years ago in a federal report describing mistakes in initial data processing. Balloon measurements are less reliable than thermometers and satellites because of sparse coverage and inconsistencies among instruments. For more on this topic, see Myth #2 in this report [PDF] by James Wang and Michael Oppenheimer.

You can read more corrections of misinformation on our Myths and Facts page.