Climate Change 101: All The Basics

It’s happening! We are hearing about climate change from all angles, but I get questions every day as a climate scientist that reveal most people don’t actually know what climate change truly is. I’ve come up with a comprehensive list of the basic facts to get you started in forming your own opinions.

Photos featured here were taken at Petrified Forest National Park! A great example of how an area can change over time with new climate conditions.

What is climate?

Climate is roughly defined as the average weather of a region for a long period of time, usually about thirty year periods. Weather is our everyday conditions – temperature, precipitation, wind, etc. Climate is different for different regions, based on latitude, elevation, and other physical components for a location.

This definition means that there is a difference between climate and weather. For example, some days it will be colder than expected, and lots of climate change deniers use those opportunities to speak out – this is not a good argument because we are concerned with the long-term averages, not a single anomaly coldfront. For this reason, “global warming” is not an accurate term to describe what’s going on; some regions are warming, but some are cooling. Climate change is uneven.


Why is our climate changing?

Earth has a process called the greenhouse effect you have probably heard about. The greenhouse effect is actually an awesome thing because it traps in some solar radiation, which keeps our planet a whopping ~33 degrees warmer than it would otherwise be[i]. Basically, there are particles in the atmosphere which prevent all that solar energy from reradiating off the Earth. Those particles are in the forms of gases.

Greenhouse gases are more specifically gases that we, as humans, have added to the atmosphere and include the ever-ominous carbon dioxide. As gas particles are added to the atmosphere, they are trapping and absorbing more solar radiation. This in turn is warming up our planet more than historically usual. Climate is changing because we are continuing to warm the Earth as more greenhouse gases are emitted to the atmosphere and trap solar energy.

What is carbon dioxide?

As discussed above, carbon dioxide, CO2, is a greenhouse gas. It traps sunlight from being reradiated into space after the solar radiation hits the Earth, and thus is a major contributor to atmospheric warming. We are relatively sure of the amount of CO2 present in Earth’s atmosphere[ii]. CO2 is created when a carbon source is burned (or “combusted”); for instance, coal is fossilized carbon, and burning coal (like for fueling power plants) releases CO2. The combustion of gasoline and petroleum for transportation is another big source of CO2. These are all fossil fuels. There are some natural processes that emit CO2, too, like volcanic eruptions, but that only equal ~1% of human emissions[iii].

Fun Fact: water vapor is actually the most abundant greenhouse gas. The issue with CO2 is that it takes a really long time to break down, and therefore warms the atmosphere more severely, while water vapor only lingers about ten days.

How do we know climate change is caused by humans?

We have a pretty good idea of what the earth looked like before humans. Ice cores essentially hold bubbles, which scientists can use to extract information about the air composition. Tree rings and geological studies, like rock sediments and fossils, also closely match up to confirm our understand of past climate. These lines of evidence, can also tell us about the climate during human times before the Industrial Revolution. Long-term records can tell us about temperature, atmospheric composition, cycles of sun, perception patterns, etc… it’s amazing!

Based on this highly confident data, plus knowledge of natural variations of the planet, scientists can run simulations to predict what the climate of the Earth should currently look like. The steep rise in temperatures following the Industrial Revolution are extremely abnormal by historical predictions[iv]. Simulations can play around with factors like the abundance of certain gases in the atmosphere or changes in the sun’s energy. There is no confirmed simulation that can explain the current temperature rise by anything other than increased carbon dioxide in the atmosphere[v].



Why is sea level rising?

There are two major processes that contribute to sea level rise: glacial melt and thermal expansion. As our atmosphere continues to warm, glaciers are melting. We’ve all seen sad National Geographic photos of a skinny polar bear on a lonely ice sheet. There are recent videos of massive calvings[vi], which is essentially when a chunk of a glacier falls right off into the ocean. These glacial fragments ultimately melt and add water to the total volume of the ocean; this is similar to having ice melt within a full cup of water – it’s eventually going to spill over once the ice melts. Thermal expansion means that warmer water takes up more physical volume than colder water. Thus, the water we already have in the oceans is expanding and taking up more space as ocean temperatures rise.



If you are wondering how you can continue to reduce your personal impact on climate change, check out this post on easy sustainable habits to adopt or this post discussing why we should think about our trash.

If you have additional climate change related questions, feel free send me a message via this contact form or via instagram dm! I would like to continue writing about science to be helpful for the non-scientist.


[i] Department of the Environment. “Greenhouse Effect.” Department of the Environment and Energy, Australian Government,

[ii] Laboratory, Oak Ridge National. “Global, Regional, and National Fossil-Fuel CO2 Emissions.” Image, Carbon Dioxide Information Analysis Center, Graphs available on this page via weblink for national, regional, and other CO2 analysis

[iii] Scott, Michon, and Rebecca Lindsey. “Which Emits More Carbon Dioxide: Volcanoes or Human Activities?” Science and Information for a Climate-Smart Nation, NOAA, 15 June 2016,

[iv] ESRL Web Team. “ESRL Global Monitoring Division News Items.” Earth System Research Laboratory, NOAA, 1 Oct. 2005,

[v] Riebeek, Holli. “Global Warming : Feature Articles.” NASA, NASA, 3 June 2010,

[vi] McCormick, Gail. “Calving Season.” Calving Season | Earthscope, NSF, Apr. 2017,


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