Climate Change For Dummies. Elizabeth May
immediately join to form carbon dioxide.
Altogether, vegetation and soil store about a billion metric tons of carbon every year, and another 1.6 billion metric tons move in and out between the land and the air. So far, the plants, animals and soil have packed away 3.3 billion metric tons.
Investigating humanity’s impact on the carbon cycle
A lot of the carbon dioxide in the atmosphere is natural (you’re breathing some out, right now), but human activities also contribute plenty of the gas (we discuss these activities in Part 2). Historically, the carbon dioxide that people put into the air was pretty much soaked up by the carbon sinks, and the amount of carbon dioxide that was around before people started building factories had been fairly steady since the beginning of human civilization.
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FIGURE 2-5: How trees and soil work side-by-side with carbon dioxide.
Producing industrial amounts of carbon dioxide
Since the Industrial Revolution went into full swing around 1850, the amount of GHGs in the atmosphere has risen drastically. Due to burning fossil fuels, as well as clearing forests, people have almost doubled the carbon dioxide emissions in just over a century, and today, carbon dioxide levels are higher than they have ever been in recorded history (see Chapter 4 for more about fossil fuels). In fact, atmospheric carbon dioxide levels are higher today — a 45 percent increase — than at any time in the past 800,000 years. (Carbon dioxide levels were much higher millions of years ago, however. We talk about the history of carbon dioxide levels in greater detail in Chapter 3.)
Carbon dioxide concentration levels are currently at about 412 ppm, and they rose at an average of 2 ppm per year between 2000 and 2021 because of increasing emissions due to human actions. On average, in the 1980s, globally, people put 7.2 billion metric tons of carbon dioxide emissions into the air every year — and those emissions have been increasing every year — now at 43 billion, per the Center for Climate and Energy Solutions. So many people are using so much energy, mostly in industrialized countries, that the amount of carbon that is being put into the air is knocking the carbon cycle off balance.
Plugging up the carbon sinks
The Earth’s carbon sinks, which used to be able to handle everything oxygen-breathing creatures could throw at them, aren’t able to keep up with humanity’s increased carbon dioxide production. Studies presented through the Intergovernmental Panel on Climate Change (IPCC) reports suggest a bunch of different possible consequences, ranging from a theory that new plants might appear that can soak up more carbon dioxide to the idea that carbon sinks may become full and may no longer be able to absorb any more carbon dioxide. Like anyone who works overtime, carbon sinks could become weaker as they soak up more carbon dioxide.
The ocean has stored carbon effectively in the past, but global warming is causing the oceans to do just the opposite. The top layers of the oceans — the top 2,300 feet (700 meters) have warmed a lot since 1900. That top layer is now 1.5 degrees Fahrenheit (0.83 degrees Celsius) warmer. Carbon dioxide is less soluble in warm water. The oceans push the carbon dioxide that they can’t dissolve into the air, instead. Data collected during the 1980s and 1990s suggested that both land and ocean sinks seemed to have kept up with growing emissions. However, more recent studies show that the carbon dioxide intake of some sinks, such as trees, is slowing down.
In addition to the warming impact, as carbon dioxide mixes in the top layers of ocean water, the oceans are getting more acidic. Carbon dioxide mixing with ocean water makes a chemical change to carbonic acid. Carbon dioxide is less soluble in warm water, so the acidification of oceans is worse in the colder regions, and this trend is super worrying. The increasingly acidic ocean makes it harder for sea creatures that live in shells to form those shells. Where Elizabeth and John live on Vancouver Island, aquaculture operations growing oysters and scallops have had to move the early stages of growing shells to the warmer waters of Hawaii, to then transport the scallops and oysters back to Vancouver Island’s colder waters to reach maturity. This increased acidity is measurable. In 2021, the oceans are 25 percent more acidic than in 1900.
Checking Out the Other GHGs
Carbon dioxide may get all the press, but 23 other GHGs (in five main groups) also heat things up. Although they’re present in much smaller amounts, these gases are actually far more potent, molecule for molecule, in terms of greenhouse effect. You might think of them as carbon dioxide on steroids. Table 2-1 shows you the power of some of these gases compared to carbon dioxide as the reference starting point with a global warming potential of 1.
TABLE 2-1 Global Warming Potential of GHGs
| GHG | Global Warming Potential Over Time | |
|---|---|---|
| 20 years | 100 years | |
| Carbon dioxide (CO2) | 1 | 1 |
| Methane (CH4) | 56 | 21 |
| Nitrous oxide (N2O) | 280 | 310 |
| Hydrofluorocarbons (HFC) Group of 13 gases | 3,327 | 2,531 |
| Perfluorocarbons (PFC) Group of 7 gases | 5,186 | 7,614 |
| Sulfur Hexafluoride (SF6) | 16,300 | 23,900 |
Source: United Nations Framework Convention on Climate Change, GHG Data, Global Warming Potentials, http://unfccc.int/ghg_data/items/3825.php
Because so many different types of GHG exist, people usually either talk about only carbon dioxide (because so much more of it exists than the others) or GHGs in terms of carbon dioxide equivalents — how small an amount of the gas you’d have to put into the atmosphere to have the same warming impact as the current level of carbon dioxide. Referring to all GHGs with this measurement makes assessing and measuring them that much easier. So, when we say “greenhouse gas” in this book, you can actually think of it as carbon dioxide equivalent emissions. No calculator needed.