Understanding Climate Change

Graphic of the sun and earth showing the greenhouse effect.
Greenhouse gases form an invisible “blanket” around earth, their molecular structure traps heat and keeps the planet warm. However, increasing emissions are making the “blanket” hotter than we are prepared to handle.


What is climate change?

Climate change refers to the alteration of climatic conditions from historic norms and the associated threats to environments and society. These threats take different forms depending on location but include more frequent and severe storms, droughts, floods, wildfires, storm surge, sea level rise, ocean acidification, increasing temperatures, changes in seasonality, animal behavior and disease transmission.

Graph showing atmospheric carbon dioxide
Fossil fuel combustion is increasing atmospheric CO2 levels at an unprecedented rate and must be curbed to prevent worsening climate change

Data: Luthi, D., et al.. 2008; Etheridge, D.M., et al. 2010; Vostok ice core

Why is our climate changing?

Earth has always experienced cycles of global climatic change, alternating between periods of high and low temperatures. These shifts are driven by a variety of natural processes and slowly occur over tens of thousands of years. They are characterized by the concentration of carbon dioxide (CO2) present in the atmosphere. CO2 is a greenhouse gas, meaning it contributes to the warming of the planet by trapping heat in earth’s atmosphere. This phenomenon is called the greenhouse effect and is necessary to keeping earth surface at inhabitable temperatures. Generally, lower atmospheric greenhouse gas concentrations mean lower temperatures, and higher concentrations mean higher temperatures.

Today, when we refer to climate change, we are not referring to the natural cycles of the planet but to anthropogenic or “human caused” climate change. Since the industrial revolution, humans have contributed to climate change by emitting immense amounts of CO2 and other greenhouse gases via the burning of fossil fuels. Pre-industrial concentrations of atmospheric CO2 hovered around 280 parts per million (ppm), current concentrations measure nearly 420 ppm the highest they’ve been in nearly 3 million years. This rapid increase in greenhouse gas emissions is trapping heat in our atmosphere causing global climates to change very drastically very quickly. These changes pose many threats that are manifesting more quickly than we can adapt to meet them.
A graph showing climate change induced temperature rises
Average global temperatures are rising rapidly, scientists agree we must limit warming below 2°C to prevent catastrophic consequences from climate changes


Is climate change the same as global warming?

Kind of. While these terms refer to the same phenomena, the term global warming paints an incomplete picture. Although data shows that the average global temperature is and has been rising consistently since fossil fuel combustion intensified during the industrial revolution, this is only one of many symptoms associated with climate change. Global warming sufficiently expresses the rising average global temperature but notably omits key factors such as sea level rise, ocean acidification, extreme weather events, and changes in rainfall, seasonality and animal behavior. Climate change is a more appropriate and holistic way of discussing the many threats posed by increasing greenhouse gas concentrations.

Additionally, while the average global temperature is rising year over year the changes are not uniform over time and space. For example, in some places winter is getting colder and harsher even if the overall average annual temperature is rising. In this case even though temperatures are rising for most of the year, “global warming” does not accurately convey the situation since some days are colder than they used to be. “Climate change” is a better term for describing the changing conditions of our environment because it is more holistic and candid in its scope and scale. (Source)

Why are climate projections always shown in ranges?

Because climate change is caused by greenhouse gas emissions, the severity of future climate threats scale with projected emissions. Higher end projections correspond to a “business as usual” emissions scenario, where emissions continue along their current pathway. Lower end projections, correspond to an emissions scenario where energy generation is entirely renewable, new carbon capture technology has been developed and transportation has been overhauled. Theoretically, even if emissions were to entirely stop tomorrow, enough greenhouse gases have already been emitted that the effects of climate change would continue to intensify, but the worst effects would be avoided. As such, it is critical to work toward lowering emissions to mitigate the severity of climate change damage.

Last updated: September 19, 2022

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