By: Bob Henson , 7:05 PM GMT on September 22, 2015
We’re in the midst of a landmark period for our changing climate: the warmest year thus far in the warmest decade in global records of surface air temperature. This is also a crucial time for dialogue on climate change, as we approach a major UN meeting in Paris this December.
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Motivating all this activity is the inexorable build-up of carbon dioxide and other greenhouse gases in our global atmosphere as a result of burning fossil fuels (coal, oil, and gas). When fossil fuels are burned, carbon from the fuel joins with an oxygen molecule from the air to create CO2. Because carbon dioxide is odorless and invisible, it’s all too easy to ignore. People had a harder time ignoring the “emissions” when our land-based transportation was conducted by horse-drawn wagon!
Despite its literal invisibility, carbon dioxide is all too real a substance, and fossil fuels add a tremendous amount of it to our atmosphere.
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Global emissions are still climbing. In the year 2013, fossil fuel use and cement production put an estimated 35.3 billion metric tons of CO2 into the air (a metric ton is about 10% greater than a U.S. ton). That’s more than twice the amount emitted in 1970. Cement production is only a sliver of this total--historically about 2-3%, but now closer to 5%. Roughly 46% of the annual emissions shown in the graphic remain in the atmosphere each year, with the rest absorbed fairly promptly by oceans and land areas.
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Nation by nation, the United States no longer leads the pack. Back in the late 1990s, the U.S. was responsible for about 30% of global CO2 emissions, while China represented about 15%. Now the roles have switched as a result of China’s breakneck pace in manufacturing and development. In 2013, China was responsible for roughly 29% of global CO2 emissions, with the U.S. at around 15%. A substantial part of China’s CO2 emissions is the result of items being manufactured for sale in the United States and elsewhere;
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Per capita, the U.S. is still in the driver’s seat. Because the United States has less than a quarter of China’s population, the amount of CO2 emitted per person is more than twice as much in the U.S. versus China. A few oil-producing nations in the Middle East have even higher per-capita rates, but their small populations means that they produce far less CO2 overall than the United States.
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Decades of emissions add up. When the atmosphere's stock of carbon dioxide goes up, it takes several hundred years for the oceans to absorb about 75 percent of this excess. The remaining 25 percent or so is stuck in the atmosphere for much longer--some of it for more than 100,000 years. This is why emissions from decades ago still have a big impact on climate.
And when it is absorbed by the oceans, it causes the water to become more acidic, which causes damage to life in the oceans.
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Of the total amount of CO2 put into the air from 1970 to 2013, the US is responsible for about 22%; the EU28, about 18%; and China, about 15%. If you go back before 1970, the United States has an even larger share of the pie.
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Progress is possible. As a group, the EU28 nations are now emitting about 14% less CO2 than they were in 1990. That’s noteworthy when you consider that the EU28’s population and level of development is roughly comparable to the United States’. Back in the early 1980s, the US and EU28 had nearly identical CO2 emissions. By 2013, the US annual total was about 43% more than the EU28’s.
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There’s no single bright line that separates a livable climate from one riddled by disaster, but for more than 15 years, many scientists and policymakers have worked toward the commonly cited goal of no more than a 2°C (3.6°F) global temperature rise above pre-industrial levels. In June, an analysis by the International Energy Agency showed that the combined global pledges thus far would allow a temperature rise of 2.6°C (4.7°F) by 2100 and 3.5°C (6.3°F) in the 2200s. Such a rise would boost the odds of irreversible physical change, such as the unstoppable melting of ice sheets. It would also raise the risk of truly serious impacts on agriculture, water and food supply, and human health, raising the specter of increased conflict and climate refugees. Some analysts are already pointing to the role of record drought in Syria as a major factor in that nation's civil war and the subsequent flood of migrants.
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New discoveries of oil, coal, and gas in recent years have led to unexpectedly abundant supplies of fossil fuel. Yet if we want to be fairly confident of avoiding the 2°C benchmark, we can only burn a small fraction of this fossil fuel--only about 20%, according to one influential estimate that was reinforced by the IPCC in 2013.
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We now know that massive amounts of energy can be produced apart from fossil fuels, with the costs steadily dropping. A group of eminent British scientists and policy leaders has called for a Global Apollo Program--an international 10-year R&D effort to make renewable energy more affordable than fossil fuel. Such efforts will go a long way toward giving any global agreement cobbled together in Paris a fighting chance to succeed.
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