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BAYCS Summary of the 2021 IPCC Report

Updated: Aug 31, 2021

By Giovanni Ocon & Oona Clark

To add to the impending doom of the climate crisis, the IPCC recently released a comprehensive climate report. The report assesses the current climate catastrophe facing humanity in a list of twelve chapters. Though the report is scientifically comprehensive and deserves a full reading, we will summarize each chapter in sufficient detail to merit an understanding of our current situation.

Chapter 1: Context of Climate Change

The 224-page chapter talks of the scientific premise of climate change, with human activity being the major driver of the phenomenon. Of such human activity, industrialization is the primary factor of such change. Though industrialization is a general term, activity related to subsequent carbon emissions and corruption of the ozone layer are most evident. The report does explicitly state that the context of climate change is partially contributed to natural factors, though rigorous methodology has proven that the majority of climate change has been caused by egregious human activity. Basically, science must account for both natural phenomena and human activity to fully comprehend the premise of climate change.

Chapter 2: Changing State of Climate Change

As climate change’s presence has been established, science must also measure its change. Climate change has been studied since the concept of climate was discovered and expanded during the 19th century. As the previous chapter stated, scientists from all parts of the world have studied climate with the use of physical principles and mathematical modeling. Even without formal modeling, humans have observed climate change since its most explicit peak. Not only have scientists measured the massive increase in climate change throughout the years, they have viewed it in Earth’s different ecosystems. In this chapter, the ecosystems mentioned are the ocean, biosphere, cryosphere and atmosphere. All of these systems have been damaged due to the exorbitant amount of greenhouse gases released.

Chapter 3: Human Influence on the Climate System

This chapter expands on the previous established context to explain the effect of human activity on natural phenomena. Like the previous chapter, this one mentions specific phenomena; Influence on atmosphere, global surface warming and large-scale temperature change. Of these phenomena, all of them have been initiated and exacerbated by human activity.

Chapter 4: Future Global Climate: Scenario-based Projections and Near-Term Information

This chapter of the report is where some of the most long-term intriguing information is written. Much of this chapter is dedicated to expressing the general projection of the future in climate change. Though this seems to be quite general, the remaining chapters are dedicated to speaking in length detail over the validity of climate change as an existential threat.

Chapter 5: Global carbon and other biogeochemical cycles and feedbacks

Following the direction of the last chapter, this chapter establishes the effects of specific carbon emissions on the previously mentioned ecosystems. The major chemicals mentioned are CO2, CH4 and N2O.

Chapter 6: Short-lived climate forcers (SLCFs)

This chapter describes short-lived climate forcers as primarily being air pollutants, such as aerosols (ex. Sulphate, nitrate, & ammonium, differing combinations of which are very common in fertilizers) and chemically reactive gases (ex. Ozone and methane, which you may recognize as greenhouse gases commonly talked about). The report states that these are called short-lived climate forcers because their effects usually take place within the first two decades of their emission or formation, and can either have a cooling or warming effect on the atmosphere. An important thing to note is that factors like these are very complicated and often multi-faceted. One thing that was mentioned in the report was that some of these aerosols which had a cooling effect actually occasionally masked the warming that was driven by greenhouse gases (line 50, pg. 13, chpt. 6).

Chapter 7: The Earth's energy budget, climate feedbacks, and climate sensitivity

This chapter discusses the idea of Earth’s energy budget, which essentially means the flow of energy that enters the Earth from the sun, and then what flows back out of it. It talks about how changes in the Earth’s atmosphere cause shifts in how this energy flow functions, and how it is connected to the rise in emissions, how much carbon the planet can take, and sea level rise, among other things. An important thing to note here is that although Earth is extraordinarily big to humans, it has a finite amount of energy and resources, just like any smaller level of ecosystem.

Chapter 8: Water cycle changes

This chapter describes how an increase in global temperature equals an increase in extreme water-related weather events, or lack thereof, examples of which we are already seeing today. They describe it as both precipitation and evaporation increases, leading the climate to flip back and forth between opposite extremes depending on the region. What this means is storms, such as snowstorms and hurricanes will and already have been getting progressively worse, and droughts will continue to persist and will get worse. Examples of these in North America are the increases in hurricanes such as the ones in Puerto Rico, and the severe droughts and heatwaves that have been plaguing the West Coast.

Chapter 9: Ocean, cryosphere, and sea level change

This chapter deals with an effect of climate change you’ve definitely heard about many times, sea level rise. One thing that is mentioned in this chapter is the different possible scenarios for increase in global temperature, the least extreme being SSP1-2.6 and the most extreme being SSP5-8.5, with some others in between. To give a comparison between the enormity of BOTH of these scenarios, the projected range in global sea-level rise for SSP1-2.6 is between 0.45 and 0.55 meters (remember, this is over the ENTIRE global oceans, which is a lot), and 1.4 to just under 2 meters for SSP5-8.5 by the year 2150.

Chapter 10: Linking global to regional climate change

In the tenth chapter the phenomena mentioned are expressed in regional-global terms. In other words, the rigorous data obtained through the report indicates how environmental degeneration not only affects individual regions, but the entire globe. IPCC’s data explains why so many disastrous phenomena have arisen in opposite parts of the world. These events are not separate, but intimately related phenomena. This chapter describes regional information in the context of large events, and lays the foundation for the next chapter.

Chapter 11: Weather and climate extreme events in a changing climate

This chapter is perhaps the most detailed in events directly related to climate change. As was mentioned before, much of the major events in the world stem from the geometric increase in emissions. As anyone who has lived in the past two decades has observed, virtually every part of the world has been devastated by a climate catastrophe. At the rate of increase in emissions, much of the Global South will be depleted in a matter of decades. The events mentioned in this chapter are temperature extremes, droughts, floods and storms.

Chapter 12: Climate change information for regional impact and for risk assessment

This is the final ominous section in the twelve-chapter report. All of the data derived from the methodology over a prescient amount of years is summarized in the projection of humanity’s future for climate. No expansion needs to be stated, though if humanity does not take climate action in the next decades it will face(faces) a decidedly existential threat.

Thanks to all who contributed this summary, here is the link to the report and informative sources:

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