Climate Science for Everyone: How much heat can the air and ocean store?

CATEGORY: ClimateTo read other articles in this series, click here.

Let’s look at how much energy the oceans can store compared to the energy storage of the atmosphere.

One way to describe the amount of energy that something can store is called “specific heat.” This is essentially the amount of energy required to heat up a mass of a material by a certain temperature. In our case, we’ll use 1 kg heated by by 1 degree Celsius (1.8° F) because those are the international standards.

The specific heat of air is about 1158 J/(kg*C) while the specific heat of seawater is about 3850 J/(kg*C), where a Joule is a standard measurement of energy. We can see that air has a specific heat a little more than 3x smaller than that of water. But we know from our day-to-day experience that water is a lot denser than air is, and that will matter a great deal to our calculations. (For reference, one Joule is about the amount of energy you need to expend to lift one pound 9 inches.)

While we could go through a huge amount of geometry to estimate how much air and seawater there is on the Earth, but there’s an easier way – use the measurements of experts. for example, this paper calculated that the total mass of the atmosphere is about 5.14 x 1018 kg, while the National Oceanic and Atmospheric Administration (NOAA) has calculated that the total volume of the world’s oceans is about 1.34 x 10^18 m3. In order to get the total mass of the world’s oceans we need an estimate of the density of seawater, which I found at this MIT link – 1027 kg/m3 (other sources have similar values).

Using this, we can multiply the mass of the atmosphere times the specific heat of the air to calculate what the total heat capacity of the atmosphere is:

5.14\times 10^{18} kg\cdot 1158\frac{J}{kg*C} = 5.95\times 10^{21}\frac{J}{C} (Eqn. 1)

In other words, it takes about 5.95 x 1021 Joules to raise the temperature of the atmosphere one degree Celsius.

For ocean we need to add one step – multiplying the volume of the water by its density to get the total mass of the ocean

1.3410^{18} m^3\cdot 1027\frac{kg}{m^3}\cdot 3850\frac{J}{kg*C} = 5.30\times 10^{24}\frac{J}{C} (Eqn. 2)

This shows that the heat capacity of the oceans is about 1000x larger than the heat capacity of the Earth’s atmosphere.

So why do we care? First, it helps to explain why we care about El Nino and La Nina cycles in the Pacific Ocean. If you’re unfamiliar with the terms, La Nina is a massive upwelling of cold water in the Pacific that, because ocean water has a much higher heat capacity than air, cools off the entire planet and affects weather patterns. El Nino is a massive pool of hot water in the Pacific that does the opposite – it dumps heat stored in the ocean back into the atmosphere, warming the globe and affecting weather patterns. Nearly all the energy absorbed by the Pacific Ocean during La Nina periods will eventually be emitted back into the atmosphere during El Nino periods.

Second, the heat capacity of the world’s oceans helps to explain why scientists are so interested in how much energy has been stored in the ocean. Since total ocean heat capacity is about 1000x greater than total atmosphere, it means that a barely measurable temperature increase in the ocean (1/1000th of a degree C) could drive a massive spike in global air temperature (1 degree C).

The difference between measured global surface temperature from various sources and the temperatures adjusted to remove the influence of El Nino, volcanoes, and the solar cycle. Note that the massive 1997/1998 El Nino spike is nearly completely the result of ocean El Nino dumping stored energy into the atmosphere. (Image Credit: Skeptical Science)

Lastly, we care because it demonstrates just why the average global temperature hasn’t been warming as fast over the last several years. We’ve had more La Nina cycles since 1998 than we’ve had El Nino cycles, and that means the Pacific ocean is storing more energy.

El Nino Southern Oscillation index.

The problem with this, however, is that it means that energy is going to come back OUT of the ocean again eventually. And when (not if) that happens next, the average global temperature will spike.

Climate Science for Everyone: heavy snows are expected in a warming world

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There are people who say that heavy snowfall means that human-caused climate disruption must be wrong. This is a misunderstanding on their part. Fortunately, it’s quite simple to correct the misunderstanding.

You can live nearly anywhere and have personal experience of how hotter air has more water vapor in it. It always feels much more humid when it’s hot than when it’s cool. My personal experience with this was visiting Connecticut in late August, when it was 95 degrees out with unbearable humidity.

It’s also the case in the winter. There’s a reason why the Front Range of Colorado (where I live) gets more snow from an upslope flow than from any other weather condition – the warm air from the Gulf of Mexico has a lot of water vapor in it, and when that air cools down as it’s forced to higher (and colder) elevations by the Rocky Mountains, the excess water vapor freezes and falls as snow. Continue reading

Climate Science for Everyone: Carbon dioxide increases in the air are mostly from burning coal, oil, and natural gas

Figure 1 – The carbon cycle

Update: To read other articles in this series, click here.

Over the last few decades, scientists have learned a lot about how life interacts with the air, land, and sea. And in the process, they’ve made observations that have demonstrated beyond any reasonable doubt that the increasing carbon dioxide in the air is from people burning coal, petroleum, and natural gas.

So how did the scientists put together all the pieces to make a complete conclusion? They started with an understanding of how plants use carbon during photosynthesis. That knowledge showed that the increased carbon dioxide in the air was from plants. Then they formulated some guesses as to where that much plant-based carbon dioxide could come from and, by process of elimination and careful accounting, determined that the source was human consumption of fossil fuels. Continue reading

Climate Science for Everyone: How scientists measure the carbon dioxide in 800,000 year old air

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Climate scientists who study the history of the Earth’s climate (also known as paleoclimatologists) know that modern carbon dioxide levels are at their highest level in the last 800,000 years. They tell us this because they’ve been able to measure the carbon dioxide in air that is actually 800,000 years old. So how do they do that?

Scientists know how much carbon dioxide was in the air hundreds of thousands of years ago because they actually have small samples of ancient air stored in glacial ice. To get a feel for how this works, consider the following examples. Continue reading

Climate Science for Everyone: Why 3% annually is actually a lot of carbon dioxide

Atmospheric CO2 concentration data from ice core (blue, 1750-1975)
and direct atmospheric measurements (red, 1960-2010) vs. “compounding
interest” model described in post (purple). Click for a larger version.

In many ways, climate science is difficult. There’s a reason that the best climate models require some of the most powerful supercomputers in the world in order to run. But the most important concepts are easily understood by a non-expert with either a little mathematical skill or the ability to use some simple online tools. This is the inaugural post of a new series that seeks to illustrate how anyone and everyone can understand the most important concepts underlying climate science and the reality that is human-caused climate disruption.

Update: To read other articles in this series, click here.

Are people adding a lot of carbon dioxide (CO2) to the atmosphere? It’s such an easy question to ask, but the answer depends on what you mean by “a lot.” And it depends on what you’re referring to. Continue reading