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.
SVANTE ARRHENIUS: EARLY CLIMATE CHANGE SCIENTIST
Swedish chemist Svante Arrhenius was the first person to predict what the future atmosphere might look like in the wake of the Industrial Revolution. In fact, in 1896, Arrhenius named it “the greenhouse effect.”
He spent many of his days (and likely nights) at the end of the 19th century calculating how the carbon released by burning coal (the major source of fuel at the time) might actually change the atmospheric carbon balance. In the end, he calculated that humanity could double the concentration of atmospheric carbon — in 3,000 years.
The fact that Earth is now closing in on doubling that concentration a little more than 100 years after Arrhenius made his calculations has nothing to do with his grasp of chemistry or math — it has everything to do with the fact that he based estimates on what he knew.
The internal combustion engine was only a speculative invention, with none in use. No cars were on the road, and Arrhenius certainly had no idea about traffic jams, drive-through windows, or airplanes. Who could have imagined today’s level of fossil-fuel consumption 125 years ago? After all, Arrhenius was a chemist, not Nostradamus! More than likely Arrhenius had no idea that human population would increase by nearly a factor of 5 from 1.6 billion in 1900 to 7.8 billion in 2020.
These sections focus on the other GHGs that also heat up the planet. Water vapor has a big impact on warming and is taken into account by climate scientists. But it’s the increase in carbon dioxide and methane that are pushing the global carbon balance into imbalance and to dangerous shifts that drive major climatic changes.
Methane (CH4)
Methane (CH4) accounts for four to nine GHGs of the overall 24 GHGs, according to the World Meteorological Organization, but it’s 21 to 56 times more potent than carbon dioxide. Methane is to carbon dioxide what an espresso shot is to herbal tea. (See Table 2-1.)
Methane naturally occurs when organic materials, such as plant and animal wastes, break down in an anaerobic environment (an environment that contains no oxygen and includes the right mix of microbes and temperature). This breakdown creates methane, along with small amounts of other gases. The stomach of a cow, a landfill site, and a marsh are all prime examples of methane-producing environments.
How methane gets into the atmosphere
Two-thirds of all the human-made methane comes from agriculture, and about half of that amount comes from rice crops. If you’ve ever seen rice being grown, you may remember that it’s planted
