Over the past 800,000 years, the levels of CO2 in the atmosphere have never exceeded 300 parts per million (ppm); yet, now we find our atmospheric CO2 hovering at around 415 ppm – and steadily rising (1). As CO2 is a greenhouse gas (GHG), it is not surprising that rising temperatures have been quick to follow. Data from the Goddard Institute for Space Studies at the National Aeronautics and Space Administration (NASA) shows the difference in average annual temperature clearly demonstrates that the earth is getting steadily warmer (2).
Furthermore, a National Oceanic and Atmospheric Administration (NOAA) report from February 2019 shows that of the 10 hottest years in recorded history, 8 have occurred in the past decade; and the top four hottest years recorded so far are 2016, 2015, 2017, and 2018, respectively (3).
Global warming is not a problem for the future anymore. This trend of climbing temperatures will prompt a worldwide increase in sea levels and the frequency of intense storms, longer drought periods, and deadlier heat waves (4). In 2013, the Intergovernmental Panel on Climate Change (IPCC) reported that warming above 2C is likely in almost all emissions scenarios (5).
Although GHG emissions play an important role, the global rise in temperature is caused by multiple factors, including the ejection of particulate matter (such as black carbon) and mass evaporation of water into the atmosphere (6,7). Both of these effects work in a similar way to GHGs, by absorbing energy from the sun and trapping it in the Earth’s atmosphere as heat (6,7). Water evaporation is particularly dangerous because of the huge natural store we have in the oceans. When the global temperature rises, water from the sea will be evaporated into the atmosphere, causing even more heating in the atmosphere, and therefore more evaporation (7). This is called a positive feedback loop where one effect aggravates the other. Once set in motion, the impacts of this may become significant, worsening the effect of the GHGs released into the atmosphere through human activity (7).
It is important to note the climate crisis affects the entire planet differently than it affects us on a local level. While the overall effect of higher GHGs on the climate is global warming of a few degrees Celsius, this can affect our local areas in a much more extreme way (8). This effect can be seen in Canada, for example, when we look at the temperature changes from 1948 to 2016. In this period, Canada experienced a warming of 1.7°C, about double the global rate; while in northern Canada, over the same period, temperatures rose by 2.3°C, around triple the global rate of warming (8). This is due to changing ocean currents and wind direction caused by increased temperatures. These are two of the five main factors influencing local climates, with the remaining being distance from the sea, distance from the equator, and shape of the land (9). As these factors change, so do temperature and precipitation patterns of regions across the globe, influencing the characteristics, duration, and severity of the seasons (9). For example, seasons in the Northwest Territories have all experienced a warming trend over the past 20 years (10). The most dramatic effects can be seen during winter, where temperatures are, on average, 4.5°C higher than the historical average since 1948, with a 20-40% increase in precipitation (10).
We know that temperature averages around the world have already begun to increase. According to the IPCC, mean temperatures globally will continue to rise over the 21st century if GHG emissions continue to steadily rise (5). The solution is clear – human emissions need to be stopped, or at least seriously reduced if we are to avoid the threat that the climate crisis poses to our Earth (5).
Observed changes in annual precipitation across Canada, 1948–2012, based on linear trends. Source: https://changingclimate.ca/CCCR2019/graphics/#pr_4621