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Climate Change 2021 Report

Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6)

“Those who are least responsible for climate change are often those that will suffer the most”


The IPCC is an extension of the United Nations and was started in 1988. Their main job is to provide scientific assessments related to climate change to policy makers world-wide. They provide options for mitigating the of effects as well as most likely outcomes for the various scenarios studied. This article is a summary of their latest report.


The report I pulled from is a 41 page summary of a 1,300-page study designed to bullet point information for policy makers. For the sake of this article, I focus on increasing global temperatures, extreme weather, and sea level rise as they are more digestible topics. I will be largely quoting highlights from the report or otherwise paraphrasing the information. My commentary is unquoted and meant to break through the scientific jargon.


Let’s get this out of the way. “Global surface temperature has increased faster since 1970 than in any other 50-year period over at least the last 2000 years. In 2019, atmospheric CO2 concentrations were higher than at any time in at least 2 million years and concentrations of CH4 and N2O were higher than at any time in at least 800,000 years. Natural drivers (non-human factors) changed global surface temperature by only 0°C to 0.1°C in this time.” In other words, this is not a natural process of the earth. Humans are the cause of climate change and its effects are happening right now.


Global Temperature Increases


“Some recent hot extremes observed over the past decade would have been extremely unlikely to occur without human influence. It is virtually certain that heatwaves have become more frequent and more intense across most land regions since the 1950s”. The graphic below shows the intensity of an average increase in global temperature’s effect on artic temperatures. Warming is “projected to amplify permafrost thawing of land ice and of Arctic sea ice in the north pole”. This is because not all warming is created equal. 2 ºC of warming globally is actually closer to 5 ºC - 7 ºC in the arctic.

You will see common benchmarks listed throughout this article. Namely 1.5 ºC, 2 ºC, and 4ºC. These scenarios are shown in the image above and will be discussed in more detail in the next section.


The figures below show the global temperatures over the previous 2000 years. The graph on the right is simply the same information, but shown over a more recent time period so the dramatic increase in temperature can be seen more clearly. The green line represents the warming which would have occurred naturally, while the yellow area is the observed average global temperature increase observed since the 1970s (around 1.2 ºC so far).


Extreme Weather Events (A Compounding Effect)


Before this topic can be discussed further, we need to discuss the 5 different scenarios explored by the IPCC study. The graphs below show 5 simulations they ran under best case, most likely cases, and worst-case scenarios. The various colored boxes each represent 1 of the 5 scenarios. Each box is the range of possible values, while the line is the average and most likely result.


SSP1-1.9 (light blue) was the best-case scenario in which we kept global temperatures from rising to 1.5ºC. One of the major take-aways from this report is that it is now considered impossible to keep global temperatures from rising below this goal. Therefore, SSP1-2.6 (the dark purple box) is the current best-case scenario of 2ºC of warming. Dark red is the worst case in which we simply continue emitting greenhouse gases as we are now.

The image above depicts all 5 scenarios as they relate to our greenhouse gas consumption over the coming decades. By continuing our current emission trajectory without any major changes, we will see a global temperature increase of almost 2.5ºC by 2050. The historical data proves every ton of CO2 emissions directly contributed to an increase in global warming.


What the graph above fails to show is the danger of each increase of 0.5ºC. This is the compound effect of global warming. “Human influence has increased the chance of compound extreme events. There will be an increasing occurrence of some extreme events unprecedented in the observational record with additional global warming, even at 1.5°C of global warming.” This phenomenon is described below.