# The Environment's New Math: How to Look at Earth Day, by the Numbers

The story of the environment can largely be told in data, various numbers that detail how the Earth is warming and how much pollution you're inhaling. Math is newly central to environmental considerations. Last summer, writer and activist Bill McKibben wrote an essay for Rolling Stone in which he outlined the mathematical argument for taking action on climate change. In short: To prevent a global temperature increase of 2 degrees Celsius, we need to hold our carbon dioxide emissions to 565 gigatons of by 2050.

Perhaps ironically cold in their matter-of-factness, those numbers tells the story of the state of the climate in a way that is tangible. It allows us to create a thermometer of sorts, like those used for fundraising at suburban middle schools — the goal being not to reach the line at its top. Earth Day is a similar sort of benchmark, a string tied around the finger of the country to remember to look at how we're doing. Here are the tools you need to make an assessment of the state of the Earth.

### Climate change

Data resources: The NOAA's monthly reports on climate

Last month, the temperature of the world's land and oceans was .58 degrees Celsius higher than the 20th century average. That alone seems innocuous. Here's another number: 337. For 337 straight months, the world has seen temperatures above the 20th century average. Meaning, as has been pointed out before, that anyone born after March 1985 — anyone 28 or younger — has never experienced a month during which global temperatures were below average for the century.

Map via NOAA.

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That data comes from the National Oceanic and Atmospheric Administration's monthly "State of the Climate" recaps, which it does for the United States and the world at large. Each month, the reports outline the raw data: the XXth hottest month, YY degrees above the 20th century average. While the report includes broader trends in the warming, they tend to be a bit buried.

Which is why a report from The Economist last month made a bit of a splash: it suggested that global warming was actually happening more slowly than scientists expected. It didn't take long for reason to be offered. It wasn't because humans were producing less greenhouse gasses. Instead, blame volcanoes, eruptions of which emitted particles that helped diffuse sunlight in the stratosphere.

Global temperatures are never uniformly distributed, as the map above shows. If it's hot in Australia, that doesn't mean it will be here. According to the NOAA, March 2013 was tied for the tenth-hottest March in recorded history globally, matching March 2006. But after seeing its hottest year on record in 2012, temperatures during March in the United States were below the 20th century average for the month.

Map via NOAA.

The surprising cold the United States experienced was primarily due to an Arctic oscillation, a shift in pressure patterns that moves Arctic air south. The NOAA notes that the oscillation index provided "the most negative value on record for March."

### Arctic ice

Data resources: The Snow and Ice Data Center, Jim Pettit's Arctic ice graphs.

But there's some thinking that the Arctic ice melt played a role, too. ThinkProgress outlines the research in detail, but the key point: while "still not settled science," three recent studies suggest that dropping ice levels also lead to colder weather.

The level of ice in the Arctic always fluctuates. From its peak, usually in March, the amount of ice melts until it reaches its minimum extent, usually in September. Last year, the amount of ice at its lowest point was the smallest volume ever recorded.

Graph via Jim Pettit.

If scientists confirm a link between that melt and colder Springs, expect more Marches like the one we just experienced.

There are other implications to the ice melt, of course. Cargo ships can now pass through the fabled Northwest passage, cutting shipment times between Asia and Europe. Last year, a major general in the U.S. Northern Command suggested that North America would soon have a new coast: the shoreline on northern Canada.

### Greenhouse gas emissions

Data resources: The EPA has a map tracking greenhouse gas emissions. The Department of Energy's Energy Information Administration tracks energy use and production.

Even as the United States produces more oil than it has in decades, the amount of carbon dioxide it creates — the most abundant type of greenhouse gas — has dropped. This is in part due to the slower economy since 2009, in part to the increased use of renewable sources, and in part due to the transition away from the use of highly polluting coal in power plants to cleaner natural gas — a transition spurred by low natural gas costs due, in part to fracking.

Graph via the EPA.

The most recent set of annual data from the EPA tracked emissions in 2011. That year, two-thirds of the country's emissions came from power plants, thanks in large part to old coal-burning plants that are old enough to have been grandfathered in under the Clean Air Act.

But there are two big question marks in the data. The first goes back to fracking — the process of injecting fluid into shale rock to break it apart, releasing methane gas. Methane is a much more potent greenhouse gas than carbon dioxide, 21 times better at trapping heat. And it's not clear how much of that methane leaks into the atmosphere during the fracking process.

Graph via the EPA.

The second question mark is the growth of emissions in other countries. Greenhouse gas emissions don't only cause warming over the country that emits them, and still-growing economies like China's and India's are producing ever-larger precentages of global carbon emissions.

### Air and water

Data resources: The EPA's large data set detailing various pollution.

We'll end on a positive note. Not all environmental issues are global, of course. Compared to the first Earth Day, in 1970, the United States has made great progress in curtailing pollution at the local level. Our air and water are far cleaner than they once were.

If you're curious about your local air and water quality, there are resources. The EPA has a robust tool providing a variety of data across the country. A bit easier to read is the agency's emissions map, allowing you to see the sources of a variety of pollution in your state. Here's the region around New York, showing certain types of fine particle emitters:

More helpful in a few months than it is now, the Natural Resources Defense Council offers an index of pollution at beaches across the country. The positive note here is this: There are lots of great beaches that are nearly free of the sorts of pollutants that can make you sick.

There is a downside. A draft report released last year indicates that the United States will soon see a lot more days during which seeking refuge in swimming will seem like a necessity, not a indulgence.

Graph via U.S. Global Change Research Program.