



Still not quite sure how climate change works? You're not alone. A survey from November 2018 showed only 71% of Americans believe climate change is real, and according to the Associated Press, almost half of those surveyed said the rise in extreme weather has them more convinced than just five years ago. A majority of both republicans and democrats believe climate change is happening.

Of Americans who believe climate change is real, only 60% believe it's is caused primarily by human activity - a significantly lower amount than the consensus of more than 97% of actively publishing climate scientist who agree climate change is real and primarily caused by human activity.

You may say, "well 3% of scientists aren't sure, so I'm not either." But, ask yourself this question: do you believe gravity is real? You may be surprised to learn that there's a small percentage of scientists who don't believe in gravity, despite the compelling evidence and consensus of more than 99% of scientists. That's what's great about science, there's always room for skepticism. However, when a majority of experts, who have spent their lives studying and understanding these topics, agree that something is real, there's no reason to cling to misplaced skepticism.

So why the discrepancy between scientific evidence of human-led climate change, and belief among the American public? Climate change is a complex working of multiple systems, from the carbon cycle and greenhouse gasses, to global temperature shifts and planetary evolution. Experts spend decades working to understand each piece of the puzzle, learning about geology, geophysics, chemistry, and climatology, so how can non-scientists be expected to understand?

In the following infographics, we'll walk you through the most important components of climate change, starting with how our planet's climate has worked for a recorded 800,000 years, then looking at what's happening now and what it means for our future.

For a more detailed explanation of how greenhouse gasses trap heat in our atmosphere, check out this page by the National Oceanic and Atmospheric Administration and National Weather Service.

Since the Industrial Revolution, we humans have been adding more and more carbon dioxide to the atmosphere, above and beyond what the natural carbon cycle would produce at any one time on its own.

"Half of human-related CO2 emissions occurred only in the last 40 years." -Union of Concerned Scientists

There are several greenhouse gasses that trap heat in our atmosphere, but none as problematic as carbon dioxide. Carbon dioxide poses a unique threat to earth's climate, because it stays in the atmosphere (influencing temperature) for thousands of years, and humans are adding more of it to the atmosphere than our planet has ever had before. The following graph shows annual figures for the different types of human-generated greenhouse gasses, with carbon dioxide from fossil fuels (gasoline, coal, oil, etc.) producing 65% of global greenhouse emissions.

The following graph shows global average temperatures as reported by the Intergovernmental Panel on Climate Change. The blue line depicts what scientists would expect to see from only natural sources, such as volcanic activity and solar radiation. The black line shows actual observations, which match closely with the red line, depicting what scientists would expect to see from natural sources plus greenhouse gasses caused by human activity.

Do we know what happens when the greenhouse effect gets out of hand, when there are too many heat-trapping gasses? Yes, we only need look to our sister planet Venus. Evidence suggests that Venus may once have had liquid water, with oceans much like ours on Earth. So what happened? Were there humans who released too much carbon dioxide into the atmosphere causing a catastrophic outcome? It's much more likely that environmental factors led to the planet's current situation.

As shown in the first infographic, liquid water in the form of rain is a crucial step in the carbon cycle. Water combines with carbon dioxide in the atmosphere, rains down, and makes its way to the ocean, where that carbon dioxide is ultimately sequestered in marine shells that get buried. This allows for a certain balance, taking greenhouse gasses out of the atmosphere and eventually returning some through volcanic eruptions. Without water, we wouldn't have the carbon cycle, and without the carbon cycle, there would be no way for our planet to remove atmospheric carbon. Instead of our oxygen-rich atmosphere, we might have a carbon dioxide atmosphere that couldn't support life as we know it.

On Venus, there is a thick carbon dioxide atmosphere. Because of the an abundance of greenhouse gasses, predominantly carbon dioxide, the surface of our sister planet averages 462 degrees Celsius - that's 864 degrees Fahrenheit. In comparison, Earth's average surface temperature until the mid-1900s was a comfortable 14 Celsius, or 57 Fahrenheit.

So what happened to Venus? Venus formed out of the same ingredients as our planet. It might have once had a liquid water ocean, and may have been habitable. But Venus is closer to the sun than we are, and because of that, it was heated just hot enough for the water on the planet to evaporate away. No water - no carbon cycle. No carbon cycle - carbon dioxide builds up in the atmosphere. From there, Venus experienced what's called a runaway greenhouse effect. Carbon dioxide built up in the planet's atmosphere indefinitely, causing soaring temperatures and a hellacious atmosphere 90 times thicker than ours.

While this greenhouse effect gone wrong was due to environmental factors, the result - too much carbon dioxide and rising global temperatures - is similar to what might happen here on Earth if we continue adding greenhouse gasses to our atmosphere without regard for the impacts it will have.

"CO2 (and other gases emitted from industrial and agricultural sources) trap heat in the atmosphere, so it is no surprise that we are now witnessing an increase in global average temperature." -Union of Concerned Scientists

The Intergovernmental Panel on Climate Change (IPCC), is a body of climate scientists from around the world who produce neutral reports on topics related to climate change. The IPCC warns that if we don't reduce our greenhouse gas emissions, Earth's surface temperature is projected to rise between 3.7-4.8 degrees Celsius by the year 2100.

In 2018, the IPCC released a special report detailing the impacts of a 1.5 Celsius rise in global average temperatures. Currently, human activities have led to approximately a 1.0 Celsius rise in the global average temperature, with temperatures projected to rise 1.5 degrees between 2030-2052.

With all this gloom and doom, it's natural to ask what we can do to mitigate carbon dioxide pollution from human activity and the corresponding global temperature rise. The most important thing we can do right now is share this important information with others, and demand our elected policy makers hold the nation and industries accountable for reducing carbon dioxide emissions. This problem is bigger than one generation, bigger than business, bigger than any nation - this problem is worldwide. But, there is hope.

"Anything else you’re interested in is not going to happen if you can’t breathe the air and drink the water. Don’t sit this one out. Do something. You are by accident of fate alive at an absolutely critical moment in the history of our planet.” -Astrophysicist Dr. Carl Sagan

Part of the work of the IPCC is to predict greenhouse gas emission might change in different situations, based on human activity. These predictions are called Representative Concentration Pathways (RCPs), and are based on factors like technological advances, population growth, changes in energy generation, land use, regional and global economic factors, and other circumstances.

The following graph shows four possible pathways. The worst case scenario is RCP8.5, shown by the red line. In this future, population rises quickly, technology stagnates, and we continue to produce greenhouse gas emissions, reaching 2,000 ppm atmospheric carbon dioxide levels just after the year 2200. The second graph, showing corresponding global temperature rise, indicates "an apocalyptic temperature rise" of 9 Celsius, or about 16 Fahrenheit, according to information from the IPCC interpreted by YaleEnvironment360.

The next-worse scenario is RCP6.0, shown in orange, shows carbon dioxide peaking around the year 2100 at 700 ppm, corresponding to a 3 Celsius temperature rise. The most optimistic pathway is RCP2.6, shown in dark blue. This scenario represents carbon dioxide in the atmosphere peaking right now, between 2010-2020. Shortly after the peak, humans would need to find a way to neutralize, or suck more carbon dioxide from the atmosphere than we produce by the year 2070.

What can we do as individuals to mitigate the effects of climate change?

Educate ourselves about climate change and share the information with others

Make an effort to reduce personal greenhouse gas emissions. You can do this by minimizing gasoline use (try biking, carpooling, or walking), and cutting out disposable plastics (which produce industrial greenhouse gas emissions when produced)

Support candidates who believe in climate change and are serious about reducing carbon dioxide emissions

If you're able to, consider going to school to study science or politics, so you can help invent solutions and create meaningful policy

FREQUENTLY ASKED QUESTIONS

If CO2 only makes up part of our atmosphere, how can it cause so much trouble?

Why does it matter that we passed a carbon dioxide threshold of 400 parts per million?

I'm still not sure if I believe in climate change, is there more evidence?

What global measurements can we assess to better understand climate change?

What happens if Earth gets 2 degrees warmer?

Why are more than 70% of American's worried about climate change?

Thanks to NASA for clips used in the video from their online Image and Video Gallery, and to the Library of Congress for the audio recording of Dr. Carl Sagan's 1990 commencement address to graduates at the University of Illinois at Urbana-Champaign, which was condensed for this article and video.