Initial Publication Date: August 27, 2018

Climate Literacy Quiz

Spanish-language version of quiz
is also available »

How's your climate literacy? The explanations beneath each question describe each concept in plain language, with links to references and teaching materials. Test your knowledge, and learn as you go.


Energy Literacy quiz
is also available »

Thank you to Dr. Aleya Kaushik for providing the scientific review for the quiz.

Most recent update to the data in this quiz: July 2021.
Wherever possible, links to current data are provided. Note that some of the data changes fairly rapidly.

1. What is the greenhouse effect?
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Answer - Certain gases in the atmosphere trap heat and warm the Earth

The greenhouse effect is a natural phenomenon. Certain gases in the atmosphere have the ability to absorb radiation that would otherwise escape into space. The greenhouse effect is somewhat like a blanket that retains your body heat and keeps you warm.

Gases that trap heat are called greenhouse gases and they include water vapor, carbon dioxide, methane, and nitrogen oxides. These gases can have potent effects even in small quantities.

Without this natural greenhouse effect, the Earth's average temperature would be below freezing!

Note that answer c, 'The tilt of the Earth changes the amount of solar energy the Earth receives,' is also true, but is not related to the greenhouse effect. Variations in the tilt and orbit of Earth do affect how much solar radiation reaches the Earth, and this is one of many natural variations in our climate system.

Note also that answer b, 'Life exhales gas that warms up the atmosphere,' is partly true. Some life forms, like humans and mammals exhale CO2, but this CO2 only recently came out of the atmosphere. Plants use up CO2 to make carbohydrates/sugar/which?, animals eat the plants and return the CO2 to the atmosphere. This is an example of a short-term process within the carbon cycle, and it balances out from year to year. By contrast burning fossil fuels rapidly releases carbon that has been stored in Earth's crust for millions of years.

Learn more from [link https://www.skepticalscience.com/breathing-co2-carbon-dioxide.htm 'Does breathing contribute to CO2 buildup in the atmosphere?'] from Skeptical Science.

This question relates to Climate Literacy Principle 2: [link /clean/literacy/principle_2.html 'Climate is regulated by complex interactions among components of the Earth system' new].

See [link /clean/educational_resources/collection/index.html?search_text=greenhouse%20effect 'teaching materials' new] about the greenhouse effect.

2. If the greenhouse effect is natural, then why is today's climate change a bad thing?

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[hidden 195301 'explanation']Answer – All of the above

While the greenhouse effect is natural and in fact, helps maintain a climate suitable for life as we know it, humans have altered a natural process. A small change in the amount of greenhouse gases in the atmosphere has a large and long-lasting effect. Furthermore, humans have changed the composition of the atmosphere over a short time span, and the resulting warming us many times faster than natural changes. We are already seeing consequences like heat waves, melting sea ice, rising sea level, increased wildfires, and increases in extreme weather.

This question relates to Climate Literacy Principle 6: [link /clean/literacy/principle_6.html 'Human activities are impacting the climate system' new].

See [link https://cleanet.org/clean/educational_resources/collection/index.html?q1=sercvocabs__129%3A%2A&q2=sercvocabs__129%3A7 'teaching materials' new] that relate to the ways that humans are affecting the climate system.


3. Which activities are the largest contributors of greenhouse gases?

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Although all of the activities on the list cause greenhouse gas emissions, transportation and electricity generation are the biggest causes.

In the USA, greenhouse gas emissions from electricity are falling as coal burning is slowly declining. Thus, the proportion of emissions from transportation has grown, and it accounted for 29% of total USA emissions in 2019, according to [link https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions 'EPA data'].

Worldwide, the breakdown is similar, although it's hard to make an exact comparison because some uses are categorized differently.

Sources

[link https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions 'Sources of Greenhouse Gas Emissions, USA'] - from the EPA, updated yearly

[link https://www.c2es.org/content/international-emissions/ 'Global Emissions'] trends and sources, from The Center for Climate and Energy Solutions

Global Historical Emissions -[link https://www.climatewatchdata.org/ghg-emissions ' interactive graph'] by Climate Watch

This question relates to Climate Literacy Principle 6: [link /clean/literacy/principle_6.html 'Human activities are impacting the climate system' new].

See [link https://cleanet.org/clean/educational_resources/collection/index.html?q1=sercvocabs__129%3A%2A&q2=sercvocabs__129%3A7 'teaching materials' new] that relate to the ways that humans are affecting the climate system.

4. How much has CO2 in the atmosphere increased since the Industrial Revolution?
 In the 10,000 years before the Industrial Revolution in 1751, carbon dioxide levels rose less than 1 percent. Since then, they've risen by:

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[hidden 195321 'explanation'] Answer: CO2 in the atmosphere has risen 49 percent since 1751.

From 1751-2018, humans added 1,611 billion tons of carbon to the atmosphere in the form of carbon dioxide. Around 80% of all human-produced carbon dioxide comes from burning coal, natural gas, oil and gasoline.

When today's CO2 trend is viewed in the context of 400,000 years of climate data, the result is even more stark. Humans have profoundly changed the composition of Earth's atmosphere, and along with that, the energy balance of the planet.


This question is from the NASA quiz, [link https://climate.nasa.gov/climate_resource_center/interactives/quizzes 'It's a Gas']. When the climate literacy quiz was originally written in 2018, the answer was 43%. NASA's original quiz was updated to reflect the continued addition of CO2 to the atmosphere, which raised the percentage to 46%. This quiz was updated in 2021 to reflect yet another increase to 49%.

To keep up with the changing composition of the atmosphere, compare the [link https://gml.noaa.gov/ccgg/trends/gl_trend.html 'current CO2 concentration'] with the pre-industrial average of 278 ppm in 1750.

Sources

[link https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide 'Climate Change: Atmospheric Carbon Dioxide'] from NOAA, Aug. 2020

[link https://climate.nasa.gov/evidence/ 'Climate Change: How do we Know?'] from NASA

[link https://nca2014.globalchange.gov/highlights/report-findings/our-changing-climate 'Our Changing Climate'] from the National Climate Assessment

This question relates to Climate Literacy Principle 2: [link /clean/literacy/principle_2.html 'Climate is regulated by complex interactions among components of the Earth system' new].

See [link /clean/educational_resources/collection/index.html?search_text=greenhouse+gases&Search=search 'teaching materials' new] about greenhouse gases.

5. How has the global average temperature changed since the Industrial Revolution?

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[hidden 195328 'explanation'] Answer: Warmer by more than 1 degree C (2.07 degrees F)

As of mid 2021, the Earth's average temperature (considering both land and water) has risen 1.19 degrees Celsius (2.14 degrees F) over the pre-industrial average (1880-1900).

Furthermore, the rate of temperature change is increasing: "The global annual temperature has increased at an average rate of 0.07°C (0.13°F) per decade since 1880 and over twice that rate (+0.18°C / +0.32°F) since 1981." (Quote from the NOAA page linked below).

NOAA's page about [link https://www.climate.gov/news-features/understanding-climate/climate-change-global-temperature 'global temperature'] provides a summary of changing temperatures; this page is updated regularly.

Sources

[link https://www.climate.gov/news-features/understanding-climate/climate-change-global-temperature 'Climate Change: Global Temperature'] from NOAA (this page is updated regularly)

[link https://climate.nasa.gov/vital-signs/global-temperature/ 'Global Temperature'] from NASA

[link https://data.giss.nasa.gov/gistemp/ 'Up-to-date temperature data and analysis'] from NASA's GISS Surface Temperature Analysis (GISTEMP v4)

This question relates to Climate Literacy Principle 4: [link /clean/literacy/principle_4.html 'Climate varies over space and time through both natural and man-made processes' new].

See [link /clean/educational_resources/collection/index.html?search_text=warming+temperature&Search=search 'teaching materials' new] about warming temperatures.


6. How does the rate of today's warming compare to previous episodes of rapid climate change on Earth?

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[hidden 195334 'explanation']Answer: Today, the Earth's climate is changing much faster than it has changed in the past.


We know that the Earth's temperature made big swings as we moved in and out of ice ages. And as rapid as those changes were, today we are warming the climate 10 times faster.

"As the Earth moved out of ice ages over the past million years, the global temperature rose a total of 4 to 7 degrees Celsius over about 5,000 years. In the past century alone, the temperature has climbed 0.7 degrees Celsius, roughly ten times faster than the average rate of ice-age-recovery warming."

"Models predict that Earth will warm between 2 and 6 degrees Celsius in the next century. When global warming has happened at various times in the past two million years, it has taken the planet about 5,000 years to warm 5 degrees. The predicted rate of warming for the next century is at least 20 times faster. This rate of change is extremely unusual." (From [link https://earthobservatory.nasa.gov/Features/GlobalWarming/page3.php?src=share 'How is Today's Warming Different from the Past?'])

"We know from past changes that ecosystems have responded to a few degrees of global temperature change over thousands of years," said Diffenbaugh. "But the unprecedented trajectory that we're on now is forcing that change to occur over decades. That's orders of magnitude faster, and we're already seeing that some species are challenged by that rate of change." (From [link https://news.stanford.edu/news/2013/august/climate-change-speed-080113.html 'Climate change on pace to occur 10 times faster than any change recorded in past 65 million years'])

It's even more interesting to note past spikes in temperature in the paleoclimate record (such as the Paleocene-Eocene Thermal Maximum ~55 million years ago) have been associated with other extreme changes such as rapid ocean acidification which was detrimental to marine life on Earth. Also, the Permian Mass Extinction was thought to have been initiated by rapid ocean warming leading to reduction in circulation, oceans going anoxic and emission of poisonous hydrogen sulfide into the atmosphere. Earth's geologic history gives us plenty of evidence that rapid swings in climate cause difficult conditions for life.

Sources

[link https://earthobservatory.nasa.gov/Features/GlobalWarming/page3.php?src=share 'How is Today's Warming Different from the Past?'] from NASA's Earth Observatory

[link https://news.stanford.edu/news/2013/august/climate-change-speed-080113.html 'Climate change on pace to occur 10 times faster than any change recorded in past 65 million years, Stanford scientists say'] from Stanford News

This question relates to Climate Literacy Principle 4: [link /clean/literacy/principle_4.html 'Climate varies over space and time through both natural and man-made processes' new].

See [link /clean/educational_resources/collection/index.html?search_text=abrupt+warming&Search=search 'teaching materials' new] that relate to abrupt warming.

7. We know that variations in Earth's orbit, solar output, and other factors cause changes in the climate. If we removed the human impacts of greenhouse gas emissions, what might the climate be doing today, on its own?

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[hidden 195340 'explanation'] Left to its own devices, the Earth would be in a minor cooling phase today. But human emissions of greenhouse gases have over-ridden natural effects and tipped the balance toward rapid warming.

Sources

[link https://www.carbonbrief.org/analysis-why-scientists-think-100-of-global-warming-is-due-to-humans 'Why scientists think 100% of global warming is due to humans'] by CarbonBrief

[link https://science2017.globalchange.gov/downloads/CSSR2017_FullReport.pdf 'Humans cause 93-123% of warming']

[link https://www.skepticalscience.com/should_earth_be_cooling.html 'Should the Earth be Cooling?'] from Skeptical Science

[link https://www.theguardian.com/environment/climate-consensus-97-per-cent/2018/feb/19/pollen-data-shows-humans-reversed-natural-global-cooling 'Pollen data shows humans reversed natural global cooling'] from the Guardian

This question relates to Climate Literacy Principle 2: [link /clean/literacy/principle_2.html 'Climate is regulated by complex interactions among components of the Earth system' new].

See [link /clean/educational_resources/collection/index.html?search_text=milankovitch%20cycles 'teaching materials' new] about orbital cycles (Milankovitch cycles) that naturally cause variations in climate.

8. When was the last time in Earth's history that CO2 was as high as it is now?

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[hidden 195346 'explanation']Answer: The last time CO2 was this high was 3 million years ago.

As of 2020, the atmosphere contained 409 to 416 parts per million of carbon dioxide. This number goes out of date quickly, as CO2 levels continue to rise; check the [link https://scripps.ucsd.edu/programs/keelingcurve/ 'latest data'] from Scripps.

Throughout all of the cool-downs and warm-ups of the last ice ages, CO2 never topped 300 ppm. So we're way above anything that happened during the ice ages. To look for the last time Earth's atmosphere had more than 400 ppm of CO2 we have to go farther back. Way farther back, to the Pliocene, 3 to 5 million years ago.

How was the climate back then? The temperature was 2 to 4 degrees Celsius (3.6 to 7.2 degrees Fahrenheit) warmer than today, and sea level was 50 to 80 feet higher!

On the other hand, there were giant camels, so that part sounds pretty good.

Sources

[link https://e360.yale.edu/digest/co2-concentrations-hit-highest-levels-in-3-million-years 'CO2 Concentrations Hit Highest Levels in 3 Million Years'] - May, 2019

[link https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide 'Atmospheric Carbon Dioxide'] from NOAA

[link https://www.sciencenews.org/article/what-pliocene-epoch-can-teach-us-about-future-warming-earth 'What the Pliocene epoch can teach us about future warming on Earth'] from Science News

This question relates to Climate Literacy Principle 2: [link /clean/literacy/principle_2.html 'Climate is regulated by complex interactions among components of the Earth system' new].

See [link /clean/educational_resources/collection/index.html?search_text=co2%20over%20time 'teaching materials' new] that relate to changes in CO2 over time.

9. Modern instruments have only been around for a little over 100 years. So how do we know what greenhouse gas concentrations (and temperature) were in Earth's past? (select all that apply)

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[hidden 195350 'explanation'] Answer – all of the above

The science of paleoclimatology uses geologic evidence to determine what the climate was like throughout Earth's history. Learn more in the video, [link https://www.youtube.com/watch?v=sGrQdLH1K74 'Our Shared Climate Future'], by scientists at the University of Colorado, CIRES. This specific question is addressed at 2:40 in the 5-minute video.

Source


[link https://www.ncdc.noaa.gov/news/what-paleoclimatology 'What is Paleoclimatology?'] from NOAA

This question relates to Climate Literacy Principle 5: [link /clean/literacy/principle_5.html 'Our understanding of the climate system is improved through observations, theoretical studies, and modeling' new].

See [link /clean/educational_resources/collection/index.html?q1=sercvocabs__129%3A%2A&q2=sercvocabs__129%3A6 'teaching materials' new] that explain how we know about climate.


10. What proportion of climate scientists has concluded that humans are the primary driver of today's climate warming?

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[hidden 195356 'explanation']Answer: 97% (or even more!)

The vast majority of climate scientists agree with the overwhelming evidence that humans are causing global warming. The reason there is a consensus of scientists is that there is a consensus of evidence.

The scientific consensus was measured by reading the abstracts of nearly 12,000 scientific papers. This exercise is easy for anyone to repeat: simply look at published papers in legitimate climate science journals, and tally up how many agree with the idea that humans are changing the climate. Or, if reading is not your thing, attend any earth science conference and listen to what scientists are saying. They are in resounding agreement – because the evidence is overwhelming.

If this is true, then why do we hear so much dissenting information? The answer is simple. Most of the claims that dismiss climate science are not based on legitimate science and are not found in peer-reviewed journals. When a paper has been peer-reviewed, that means it has been evaluated by a number of qualified scientists and found to have followed legitimate scientific methods (From [link http://theconsensusproject.com 'the Consensus Project']).

Source
s

[link http://iopscience.iop.org/article/10.1088/1748-9326/8/2/024024 'Quantifying the consensus on anthropogenic global warming in the scientific literature']

[link http://theconsensusproject.com 'The Consensus Project']

This question relates to Climate Literacy Principle 5: [link /clean/literacy/principle_5.html 'Our understanding of the climate system is improved through observations, theoretical studies, and modeling' new].

See [link /clean/educational_resources/collection/index.html?q1=sercvocabs__129%3A%2A&q2=sercvocabs__129%3A6 'teaching materials' new] that explain how we know about climate.

11. The most common misunderstanding about climate change is that the Earth's climate has changed naturally in the past, therefore humans are not the cause of global warming. That is not correct. What are some analogies or rebuttals that help debunk this myth?

[hidden 195359 'explanation']Possible answers

At the heart of this misconception is the idea that if something happens naturally, then it can only happen naturally. But of course that's not true. Here are some examples.

Forest fires occur naturally. Does that mean that arson is a hoax?

People die of natural causes. But sadly, people are sometimes murdered. But if people can die on their own does that mean that murder does not happen?

It rains, which makes my lawn wet. But sometimes, a sprinkler is used to make the lawn wet. So the lawn can become wet for either natural or human-caused reasons.

Rivers have always flooded. But some floods are either caused by, or made worse by human actions. If a dam ruptures, the resulting flood is because of humans – not because floods happen on their own.

Many processes on Earth have more than one cause. The presence of a natural cause does not negate the reality of a human trigger.

Furthermore, the fact that climate has changed on its own gives us some very helpful information. Throughout geologic history, we know that more greenhouse gases in the atmosphere equates to a warmer climate, regardless of the source of the greenhouse gases (from the ocean, from wildfires, from volcanoes, from melting permafrost, etc.). So as humans add CO2 and other greenhouse gases to the atmosphere, we know that it also has the same warming effect. The physical process is the same either way.

Lastly, a key difference between past climate changes and today's climate change is the rate of change. Today's warming is much more rapid that past shifts in climate. This makes it harder for ecosystems to adapt.

In past geological ages the drivers of climate have been natural (volcanoes, plate tectonics, meteorites, cyanobacteria evolving and putting oxygen into our atmosphere, etc.), but now we as humans are the drivers of climate. This is why some scientists refer to today's geological era as the 'Anthropocene.' While it is scary to think that we as a species are responsible for altering the climate, it also highlights the fact that we humans are the first 'self-aware' climate driver and so could potentially do something about our actions.

Watch Katharine Hayhoe's lively explanation for this misconception:

This question relates to Climate Literacy Principle 4: [link /clean/literacy/principle_4.html 'Climate varies over space and time through both natural and man-made processes' new].

Even though this is a scientific question, sometimes the communication is more challenging than the science. See [link /clean/educational_resources/collection/index.html?search_text=climate%20communication 'teaching materials' new] about climate communication.


12. Which country has emitted the most CO2 over time? In other words, which nation has the most responsibility for the greenhouse gases that are currently residing in the atmosphere?

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Animation of cumulative greenhouse emissions, by CarbonBrief
Answer: USA

While China is currently the largest emitter of greenhouse gases, cumulative emissions are an important way to look at our overall contribution to global warming.

China's greenhouse gas emissions per year have only recently surpassed the US. Over time, the USA has been the largest emitter of greenhouse gases to the atmosphere. In fact, we've emitted twice as much CO2 as China.

This matters because greenhouse gases have a long life span in the atmosphere. CO2 in the atmosphere lasts for 50 to 100 years or more (as explained in [link https://www.yaleclimateconnections.org/2010/12/common-climate-misconceptions-atmospheric-carbon-dioxide/ 'this article in Yale Climate Connections']). The reason why it's so important to curb emissions quickly is because greenhouse gases have a long-lasting effect. It's also why we can't sit back and blame China for their high emissions. All nations need to work together to address climate change.

Sources

[link https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions#annual-co2-emissions 'Our World in Data ']offers a particularly helpful discussion of greenhouse gas emissions from the USA, China, and other countries. (2017)

[link https://wri.org/blog/2014/11/6-graphs-explain-world%E2%80%99s-top-10-emitters '6 Graphs Explain the World's Top 10 Emitters'] from World Resources Institute, 2014

[link http://www.wri.org/blog/2017/04/interactive-chart-explains-worlds-top-10-emitters-and-how-theyve-changed 'Interactive chart of top greenhouse gas emitters'] from World Resources Institute, 2017

[link https://en.wikipedia.org/wiki/List_of_countries_by_carbon_dioxide_emissions 'List of Countries by CO2 Emissions'] - Wikipedia

This question relates to Climate Literacy Principle 6: [link /clean/literacy/principle_6.html 'Human activities are impacting the climate system' new].

See [link /clean/educational_resources/collection/index.html?search_text=co2%20emissions 'teaching materials' new] about CO2 emissions.

13. How long does CO2 remain in the atmosphere?

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[hidden 195368 'explanation']Answer: CO2 remains in the atmosphere for up to 200 years, or more.

As you know from the carbon cycle, some processes, like photosynthesis, use up carbon dioxide quickly, while others, like carbon dioxide captured by weathering of rocks, operate over many thousands of years. Thus, you can't put your finger on the exact life span of a given molecule of CO2 in the atmosphere.

The bottom line is that once emitted, CO2 continues to affect the climate for decades to millennia. That's why reducing emissions quickly is important. Because of the existing CO2 in the atmosphere, the Earth will continue to warm even after we stop burning fossil fuels.

The complexity of CO2 residence time is summed by Zeke Hausfather in [link https://www.yaleclimateconnections.org/2010/12/common-climate-misconceptions-atmospheric-carbon-dioxide/ 'Yale Climate Connections']:

"Using a combination of various methods, researchers have estimated that about 50 percent of the net anthropogenic pulse would be absorbed in the first 50 years, and about 70 percent in the first 100 years. Absorption by sinks slows dramatically after that, with an additional 10 percent or so being removed after 300 years and the remaining 20 percent lasting tens if not hundreds of thousands of years before being removed."

IPCC uses an estimate of 5 to 200 years, noting, "No single lifetime can be defined for CO2 because of the different rates of uptake by different removal processes."

Sources

[link https://www.yaleclimateconnections.org/2010/12/common-climate-misconceptions-atmospheric-carbon-dioxide/ 'Common Climate Misconceptions: Atmospheric Carbon Dioxide'] from Yale Climate Connections

[link https://www.ipcc.ch/ipccreports/tar/wg1/016.htm 'Attributes of Greenhouse Gases'] from IPCC

[link https://www.skepticalscience.com/co2-residence-time.htm 'CO2 emissions change our atmosphere for centuries']

This question relates to Climate Literacy Principle 2: [link /clean/literacy/principle_2.html 'Climate is regulated by complex interactions among components of the Earth system' new].

See [link /clean/educational_resources/collection/index.html?search_text=residence%20time 'teaching materials' new] about the residence time of CO2.

14. If we stopped burning fossil fuels today, what would happen to the climate?

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[hidden 195375 'explanation']Answer: Temperatures would stop increasing once greenhouse gas concentrations stopped increasing.

The science is evolving on this question, and this quiz was updated in 2021 to reflect those changes. Among all the bad news on climate change, this is a bit of good news. There is general agreement among scientists that when emissions fall to net zero, then the amount of greenhouse gases in the atmosphere will stop increasing. At that point, the global increase in temperature will slow or stop.

Carbon Brief has an excellent, well-referenced [link https://www.carbonbrief.org/explainer-will-global-warming-stop-as-soon-as-net-zero-emissions-are-reached 'article'] that explains why the science - and the messaging - around this topic has changed.

There are a few factors to keep in mind:

This remains an active area of climate research.

This question relates to Climate Literacy Principle 2: [link /clean/literacy/principle_2.html 'Climate is regulated by complex interactions among components of the Earth system' new].

15a. This is a graph of carbon dioxide in Earth's atmosphere, measured since 1958. There are two patterns in this data, what are they?

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Go on to the next question to learn more about this data and what it means.

This data is from [link https://scrippsco2.ucsd.edu/graphics_gallery/mauna_loa_record/mauna_loa_record_smooth_curve.html 'Scripps'], and current CO2 data and many other forms of atmospheric CO2 data are available from the website and from the related [link https://scripps.ucsd.edu/programs/keelingcurve/ 'Keeling curve'] website.

This question relates to Climate Literacy Principle 5: [link /clean/literacy/principle_5.html 'Our understanding of the climate system is improved through observations, theoretical studies, and modeling' new].

Learn more with a visualization from NOAA: Time History of Atmospheric CO2 (more info)

See [link /clean/educational_resources/collection/index.html?search_text=keeling%20curve 'teaching materials' new] about the Keeling curve.

15b. Based on the graph in question 15, What causes the annual up-and-down fluctuation in CO2 in the atmosphere?

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[hidden 195386 'explanation']Answer: Plants take up more CO2 during the Northern Hemisphere summer

The 'seesaw' of carbon dioxide in the atmosphere is caused by the changing seasons. During the summer in the Northern Hemisphere, plants and marine algae take up CO2 through photosynthesis. As plants use up CO2, it's temporarily drawn down from the CO2 in the atmosphere. In the fall, plants slow down their uptake of CO2, and CO2 is released from soils. This process is dominated by the Northern Hemisphere because there is more land mass in the Northern Hemisphere.

This question relates to Climate Literacy Principle 3: [link /clean/literacy/principle_3.html 'Life on Earth depends on, is shaped by, and affects climate' new].

Learn more with a visualization from NOAA: Time History of Atmospheric CO2 (more info)

See [link /clean/educational_resources/collection/index.html?search_text=seasonal+fluctuation+of+co2 'teaching materials' new] about the seasonal fluctuation of CO2.

15c. What is the primary cause of the overall rising trend in CO2 in the atmosphere?

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[hidden 195387 'explanation'] Answer: The increase in CO2 is caused by burning of fossil fuels.

The evidence is absolutely clear on this one. Humans have burned ever-increasing amounts of fossil fuels since the industrial revolution. Over this same time scale, CO2 concentrations in the atmosphere have risen similarly. Isotope studies show the excess carbon in the atmosphere is plant-based carbon that had been locked away in Earth's crust until recently. If the increase in CO2 were coming from the oceans or melting permafrost, it would have a different isotopic signature.

That said, warming oceans and melting permafrost also release CO2. These are examples of self-reinforcing cycles, also known as a positive feedback cycles. But the oceans are warming and permafrost is thawing because of human emissions of greenhouse gases. They are not driving the cycle, they are responding to changes caused by humans.

Sources

[link http://www.realclimate.org/index.php/archives/2004/12/how-do-we-know-that-recent-cosub2sub-increases-are-due-to-human-activities-updated/ 'How do we know that recent CO2 increases are due to human activities?']

[link https://scripps.ucsd.edu/programs/keelingcurve/2018/09/19/is-the-current-rise-in-co2-definitely-caused-by-human-activities/ 'Is the Current Rise in CO2 Definitely Caused by Human Activities?'] (answer: yes!) Response written by geochemist Ralph Keeling

[link https://scripps.ucsd.edu/programs/keelingcurve/ 'Current CO2 readings, updated daily']

[link https://www.esrl.noaa.gov/gmd/ccgg/trends/history.html 'History of atmospheric carbon dioxide from 800,000 years ago until January, 2016'] - an intriguing visualization

[link https://scripps.ucsd.edu/programs/keelingcurve/2017/10/19/video-new-animation-of-keeling-curve-available/ 'Keeling curve video from Scripps']

This question relates to Climate Literacy Principle 6: [link /clean/literacy/principle_6.html 'Human activities are impacting the climate system' new].

See [link /clean/educational_resources/collection/index.html?search_text=atmospheric+co2+concentrations 'teaching materials' new] about atmospheric CO2 concentrations.

16. What are the major causes of sea level rise? (there is more than one correct answer)

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[hidden 195406 'explanation'] Answers: Melting glaciers and ice sheets and seawater expanding as it gets warmer (also known as thermal expansion).

From [link https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level 'NOAA Climate.gov']:

"Sea level is rising for two main reasons: glaciers and ice sheets are melting and adding water to the ocean and the volume of the ocean is expanding as the water warms. A third, much smaller contributor to sea level rise is a decline in water storage on land—aquifers, lakes and reservoirs, rivers, soil moisture—mostly as a result of groundwater pumping, which has shifted water from aquifers to the ocean.

"From the 1970s up through the last decade, melting and thermal expansion were contributing roughly equally to the observed sea level rise. But the melting of glaciers and ice sheets has accelerated, and over the past decade, the amount of sea level rise due to melting—with a small addition from groundwater transfer and other water storage shifts—has been nearly twice the amount of sea level rise due to thermal expansion."

Sources

[link https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level 'Climate Change: Global Sea Level'] from NOAA Climate.gov

[link https://oceanservice.noaa.gov/facts/sealevel.html 'Is Sea Level Rising?'] from NOAA National Ocean Service

This question relates to Climate Literacy Principle 7: [link /clean/literacy/principle_7.html 'Climate change has consequences for the Earth system and human lives' new].

See [link /clean/educational_resources/collection/index.html?search_text=sea+level+rise 'teaching materials' new] about sea level rise.

17. What causes ocean acidification?

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[hidden 195408 'explanation'] Answer: CO2 dissolved in ocean water.

Ocean acidification is sometimes called "the other carbon dioxide problem." The oceans have absorbed 25 to 30 percent of the CO2 released into the atmosphere.

The increase in dissolved CO2 makes the ocean water more acidic (lowering the pH). This matters because many organisms in the ocean – from coral reefs to clam shells to plankton – build shells from calcium carbonate that is dissolved in ocean water. More acidic water makes it harder for these animals to build and maintain their shells.

Since the industrial revolution, the pH of seawater has fallen from 8.2 to 8.1 – a decrease of 0.1 pH units. While that may not sound like much, it's a 30% increase in acidity. It's also important to note that the oceans are not acidic overall. The pH of ocean water is above 7, which is means it's basic, not acidic. But ocean acidification is making the water less basic – - or more acidic. For many organisms, this is a dramatic change in the conditions they are adapted for. The current drop in pH is the fastest known change in ocean chemistry in the past 50 million years. ([link http://ocean.si.edu/ocean-acidification 'Reference'])

Why does this matter? From [link http://www.noaa.gov/resource-collections/ocean-acidification 'NOAA's ocean acidification education page']:

"Ocean acidification is currently affecting the entire world's oceans, including coastal estuaries and waterways. Today, more than a billion people worldwide rely on food from the ocean as their primary source of protein. Approximately 20% of the world's population derives at least 1/5 of its animal protein intake from fish. Many jobs and economies in the U.S. and around the world depend on the fish and shellfish that live in the ocean."

Sources

[link http://www.noaa.gov/resource-collections/ocean-acidification 'Ocean Acidification'] from NOAA

[link https://oceanservice.noaa.gov/facts/acidification.html 'What is Ocean Acidification'] from NOAA

[link http://ocean.si.edu/ocean-acidification 'Ocean Acidification'] from the Smithsonian

This question relates to Climate Literacy Principle 7: [link /clean/literacy/principle_7.html 'Climate change has consequences for the Earth system and human lives' new].

See [link /clean/educational_resources/collection/index.html?search_text=ocean+acidification&Search=search 'teaching materials' new] about ocean acidification.

18. What is the leading cause of coral bleaching?

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[hidden 195410 'explanation'] Answer: warm water

From [link https://oceanservice.noaa.gov/facts/coral_bleach.html 'NOAA's National Ocean Service page']:

"Warmer water temperatures can result in coral bleaching. When water is too warm, corals will expel the algae (zooxanthellae) living in their tissues causing the coral to turn completely white. This is called coral bleaching. When a coral bleaches, it is not dead. Corals can survive a bleaching event, but they are under more stress and are subject to mortality."

"A healthy, resilient reef can either resist a stressful event, like bleaching, or recover from it. When a coral bleaches, it is not dead. Corals can survive if water temperatures return to normal quickly."

Source

[link https://oceanservice.noaa.gov/facts/coral_bleach.html 'What is Coral Bleaching?'] from NOAA

This question relates to Climate Literacy Principle 7: [link /clean/literacy/principle_7.html 'Climate change has consequences for the Earth system and human lives' new].

See [link /clean/educational_resources/collection/index.html?search_text=coral+bleaching&Search=search 'teaching materials' new] about coral bleaching.


19. Many of us are already familiar with solutions to climate change. While there are many actions we can take every day, it's important to focus on the solutions with the biggest result. Most of the actions show below will reduce emissions, but which will have the biggest effect? There are several correct answers.

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[hidden 195412 'answer']

Switching energy sources away from fossil fuels, wasting lass food, and adopting a plant-based diet, and restoring tropical forests are all key solutions for limiting climate change. Educating girls and family planning are is another solution that can reduce greenhouse gas emissions.

See the full list of solutions from [link https://www.drawdown.org/solutions/table-of-solutions 'Project Drawdown']. This list is continuously updated, and this quiz question was updated in 2021 and is subject to change as we learn more.

Large-scale, systemic change is needed to address climate change, and changes made on a personal level are not enough to solve the problem. Nonetheless, adopting a cleaner lifestyle offers the simultaneous benefits of emitting fewer greenhouse gases while also illustrating the scale and effectiveness of various solutions. These CLEAN resources involve reductions in personal energy use:

The Lifestyle Project (more info)

How Much Energy is on My Plate? (more info)

Source

[link https://www.drawdown.org/solutions/table-of-solutions 'Project Drawdown – Solutions']

This question relates to Guiding Principle of Climate Literacy: [link /clean/literacy/guiding_principle.html 'Humans can take actions to reduce climate change and its impacts' new].

See [link /clean/educational_resources/collection/index.html?q1=sercvocabs__129%3A%2A&q2=sercvocabs__129%3A1 'teaching materials' new] about actions to reduce climate change.

20. How fast to we need to stop burning fossil fuels to limit global temperature rise to 2 degrees C? (3.6 degrees F)

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[hidden 195414 'explanation']Answer: We need to stop burning fossil fuels by 2040.

Climate scientists Stefan Rahmstorf and Anders Levermann estimated that we need to dramatically decrease emissions starting by 2020 and drop off quickly to near zero by around 2040.

This quiz question was written in 2018. The 'deadline' of 2020 has come and gone, so we can observe our progress on reducing emissions. The world consumed less fossil fuels in 2020, and [link https://www.bp.com/en/global/corporate/energy-economics/statistical-review-of-world-energy/primary-energy.html 'less energy overall'], largely due to the Covid-19 pandemic. So far in 2021, it appears that consumption is rebounding past 2020 levels. If we intend to minimize dramatic effects on Earth's climate system, we face a monumental challenge to overhaul the world's energy use within just a few years.

Note that there are other factors that can influence this estimate, such as CO2 removal from the atmosphere. The degree to which direct carbon capture could reduce the buildup of atmospheric greenhouse gases remains speculative at this point.

In 2017 Rahmstorf and Levermann concluded, "It is still possible therefore to meet the Paris temperature goals if emissions peak by 2020 at the latest.... We will need an enormous amount of action and scaled up ambition to harness the current momentum in order to travel down the decarbonisation curve at the necessary pace; the window to do that is still open."

Since the statement above was made, emissions have risen, fallen, then risen again.

Sources

[link https://www.bp.com/en/global/corporate/energy-economics/statistical-review-of-world-energy/primary-energy.html 'BP Statistical Review of Energy 2020'] | Self-updating graphs showing [link https://www.bp.com/en/global/corporate/energy-economics/energy-charting-tool-desktop.html 'annual trends in energy use'].

[link http://www.realclimate.org/index.php/archives/2017/06/why-global-emissions-must-peak-by-2020/comment-page-4/ 'Why global emissions must peak by 2020']

[link https://www.carbonbrief.org/unep-1-5c-climate-target-slipping-out-of-reach '1.5C climate target slipping out of reach'] - by CarbonBrief

[link https://www.unenvironment.org/interactive/emissions-gap-report/2019/ 'Emissions Gap Report 2019'] - Interactive report with excellent graphics, by the UN Environment Programme

This question relates to Guiding Principle of Climate Literacy: [link /clean/literacy/guiding_principle.html 'Humans can take actions to reduce climate change and its impacts' new].

See [link /clean/educational_resources/collection/index.html?search_text=renewable%20energy 'teaching materials' new] about renewable energy.

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