The science of climate change

Over my academic career I have worked towards cultivating science communication skills. Bridging the gap between the scientific community and the public is something that I am passionate about. But “science” is a broad topic – so I’ve chosen to primarily focus on the largest phenomenon impacting our world: climate change. I want to spend my life researching how climate change is impacting species’ spatial ecology, but what good is that information unless I share it? So, I also spend time teaching people about climate change in public settings to increase awareness of its importance and to teach ways we can all help to mitigate it. In these settings, it always strikes me as to how often listeners are unaware of the actual science behind it – in other words, the public often does not know what climate change actually is, and how humans caused it. It’s only been recently that I have started to ask myself why that is.

I have come to realize that the reason why I didn’t understand this is because I have been lost in my own privilege. For over ten years now I’ve been in some sort of post-secondary education learning about environmental topics or working in jobs related to the environmental field. That means that for a decade, whether or not I was fully aware of it in the moment, my mind was constantly being expanded with new information regarding climate change, the environment, or other conservation-related topics. Academics are constantly learning new information that is often not even available to the general public. Peer-reviewed literature is hidden behind paywalls, formal post-secondary education is not accessible to everyone, and the topic of climate change, for example, has only recently been introduced into the Canadian public school system (even today, in the public school science curriculum for British Columbia, the phrase “climate change” is not introduced until Grade 7). I distinctly remember learning about “global warming” in a Grade 11 Geography class (read: not until I was 16) and it was only briefly mentioned. I remember being absolutely floored by it, yet hardly any of my peers were. Thankfully, my Geography teacher took the time to sit down and talk about it with me further (thank you, Mr. Gibson). These lessons stuck with me, and I credit them (and that teacher), for helping me find this career path later in life. But, it is a privilege that I have this information readily available to me now. Academics, myself included, need to remember that our education is a privilege. All of this is to say that of course the general public does not understand a phenomenon as complex and nuanced as climate change. The average person was never given the opportunity to learn it.

But this is part of the problem. How can we effectively work towards mitigating something if we don’t care about it, and how can we possibly care about something we don’t understand?

So, what is causing climate change?

There is really only one phenomenon you need to know to understand the basic science of climate change. And that is the greenhouse effect1-4. We all understand that our atmosphere is made up of different gases that play a role in our climate or the ability for life to exist on Earth. What makes some of them greenhouse gases is the way that they chemically interact with the sun’s radiation. Most gases in the atmosphere are transparent to the energy emitted from the sun’s surface – in other words, the sun’s energy passes through them, which allows it to hit Earth’s surface. At that point the energy is absorbed and/or reflected back into the atmosphere as heat. When reflected, this heat can either pass right through those gases again or it can be trapped. Gases that are not greenhouse gases allow sun’s energy to pass through – they’re transparent to this radiated energy – and this heat then heads back out into space. Greenhouse gases, however, are opaque to this heat – they trap it and stop it from leaving our atmosphere. This process is naturally occurring and is actually vital for life on Earth. Without the greenhouse effect, the average temperature of Earth’s surface would be approximately -15°C. For reference, the current average temperature is about 15°C (a 30°C difference!). Without the greenhouse effect, Earth would be simply unliveable.

The problem is that humans have been putting too much greenhouse gases into the atmosphere, which is exacerbating the greenhouse effect1-4. More and more heat is being trapped and it’s causing the surface temperature of the Earth to increase. The greenhouse effect is necessary, yes. But we’re altering the way it should be naturally occurring – we are literally changing the way that our atmosphere operates.

But how do we know this?

Humans have been directly measuring Earth’s global average surface temperature for about 150 years5. To do so, we take an average of a variety of measurements across the world. From this data, we know that there has been a consistent warming trend since the mid-1800s5-6. Not only are these temperatures unprecedented in the last 2000 years, but the rate that the temperature is increasing is unparalleled7. We know this because we can compare these direct measurements to historical temperatures using proxy data – in other words, we use measurements of other things to determine what the climate may have been like. For example, ice cores8 or tree rings can tell us information about the climate or what the temperature may have been at a certain time in Earth’s history9.

This graph is from the 6th Assessment Report by the Intergovernmental Panel on Climate Change (learn more about the IPCC here). It compares observed global surface temperatures (green) to historical datasets (red and black). Scientists have reconstructed (black) global surface temperatures using paleoclimate records (i.e., tree rings or ice cores) and simulated them (red) using statistical models. The observed (green) data is only available for more recent years, but we can use it to validate these other datasets. Essentially, since the black and red datasets match up with the observed (green) surface temperature trends now, it tells us that they are correctly illustrating historical trends prior to this current period. From this, it is clear that there has been a rapid increase in surface temperatures in the last couple hundred years.

Humans have been directly measuring the amount of carbon dioxide (CO2), one of the primary greenhouse gases, in the atmosphere since 19501,10. To understand CO2 levels before then, we use proxy data as well. The air bubbles within ice core samples, for example, can tell us the amount of carbon dioxide thousands of years ago10 and samples from coral reefs or sedimentary rocks can tell us even farther back than that9. All of this data illustrates that the amount of carbon dioxide in the atmosphere has been increasing over time. In fact, for as far back as we can see, we have never had the current levels of carbon dioxide in our atmosphere9. Since we know the approximate start of this increase in CO2, we can trace that date to what was happening on the earth at that time – and low and behold, it coincides with the industrial revolution1,11. Once humans understood how much energy we could obtain from burning fossil fuels, we started to burn it at rapid rates – and we haven’t stopped since. When we burn fossil fuels, carbon is released into the atmosphere and combines with oxygen to create carbon dioxide1. It’s a simple chemical equation.

“This graph, based on the comparison of atmospheric samples contained in ice cores and more recent direct measurements, provides evidence that atmospheric CO2 has increased since the Industrial Revolution.” NASA Global Climate Change: How do we know climate change is real?9

Many climate change deniers argue that the correlation between increasing temperatures and increasing greenhouse gases is a coincidence. Instead, they believe that there are other natural cycles at play, such as fluctuations in the sun’s energy or changes in Earth’s axis tilt, that are affecting the temperature of our planet. This is simply not the case and these myths have been proven wrong many times before (I will write about some of these myths in future posts or you can check out Skeptical Science). The most frustrating part of all this is that scientists warned us decades ago that CO2 levels were increasing and that it might have negative consequences for our planet9. The only way to truly stop climate change in its tracks is to stop the burning of fossil fuels.

Okay, but so what? Wouldn’t warmer temperatures be more enjoyable in many parts of the world?

Unfortunately, climate change isn’t simply creating a tropical utopic planet. This is why we stopped calling it “global warming” and started calling it “climate change”12. The increasing temperatures are not just seen on land, but in our oceans9. It’s affecting where all plants and animals are able to survive. We’re seeing the melting of snow, glaciers, and sea ice – some of this melting is causing the sea level to rise and some affects our freshwater availability. Extreme natural events are increasing in frequency and intensity, and the ocean is becoming more acidic… The natural world is changing at a rate never seen before, and we are the cause of it.

But all of these impacts are for future posts. For now, you understand the science behind this phenomenon a little bit more. We live on a planet that is liveable only because of its atmosphere, yet we are altering it. It is up to us to do something about it.

As always, don’t just trust my word. Below are resources where you can learn more. None of the sources I have included are peer-reviewed literature. Instead, I have curated an assortment of publicly-available reliable sources from some of the world’s leading scientific organizations. Not all important information is hidden in university libraries – these organizations work hard to get this information out there for the public’s best interest. Please read it for yourself.

  1. NASA Global Climate Change. (n.d.). The causes of climate change.
  2. NASA Global Climate Change. (n.d.). What is the greenhouse effect?
  3. United States Environmental Protection Agency. (2022). Basics of climate change.
  4. University Corporation for Atmospheric Research. (2022). The greenhouse effect.
  5. Massachusetts Institute of Technology: Ask MIT Climate. (2021). When scientists say the Earth has warmed by 1°Celsius, which parts of the planet are being measured?
  6. NASA Earth Observatory. (n.d.). World of Change: Global temperatures.
  7. Intergovernmental Panel on Climate Change. (2022). AR6 Summary for policymakers.
  8. National Science Foundation’s Ice Core Facility. (n.d.). About ice cores.
  9. NASA Global Climate Change. (n.d.). How do we know climate change is real?
  10. Massechusetts Institute of Technology: Ask MIT Climate. (2021). How are gases in the atmosphere analyzed and measured?
  11. United States Environmental Protection Agency. (2022). Causes of climate change.
  12. National Oceanic and Atmospheric Administration. (2015). What’s the difference between global warming and climate change?

2 responses to “The science of climate change”

  1. Well done! You hit on all the main points. I also follow Skeptical Science. A great site. I look forward to seeing more of your communication on this topic. I would be particularly interested on the implications of climate change for Canada. People often forget that Canada has the longest coastline in the world and rising sea levels as well as melting permafrost will have major implications for Canada.

    Liked by 1 person

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