The Earth and the Moon as seen from Voyager 1 image courtesy of NASA.

The Intergovernmental Panel on Climate Change’s (IPCC) Fifth Assessment Report concluded after reviewing 9,200 peer-reviewed studies that there’s at least a 95% chance that global warming is primarily caused by human activities. The IPCC said in its 2007 report that there was a 90% chance global warming was caused by humans, but alternate explanations for climate change have been ruled out since then. The IPCC found that the global mean surface temperature has increased an average of 0.12 °C ( 0.22 °F) a decade since 1951. The report said that the evidence for the long-term warming trend is robust and attributed the fact that the mean global surface temperature has grown somewhat more slowly in recent years to natural variability caused in part by a strong El Niño in 1998. A number of recent studies have suggested that the deep oceans may temporarily be absorbing more heat as part of natural decadal climate cycle. The IPCC report found that sea levels have risen 19 cm since 1901 and that the pH of ocean water has decreased by a tenth of point—corresponding to a 26% increase in the concentration of hydrogen ions—since the before the Industrial Revolution. The report estimated that in order to have a 66% chance of limiting the global temperature change to less than 2° C (3.6 ° F) we would have to limit total carbon dioxide emissions to about 1000 gigatons of carbon. As of 2011, about 531 gigatons of carbon had already been emitted. Burning all the fossil fuels in known reserves would release around 2,800 more gigatons of carbon.

A new study led by James Hansen concluded that burning all the world’s available fossil fuels would raise global temperatures 16° C (29° F) over a thousand years—raising temperatures as much as 30° C (54°F) at the poles—and make the planet “practically uninhabitable”. Hansen et al. wrote that the fate of humanity may depend on whether we move to carbon-free energy or to unconventional fossil fuels and coal as conventional fossil fuels begin to be depleted. The US Environmental Protection Agency (EPA) proposed rules limiting carbon emissions from new coal and gas power plants. Under the rules, new coal-fired power plants would have to limit emissions of carbon dioxide to 1,100 pounds per megawatt hour. Right now the average coal plant in the US emits almost 1,800 pounds of carbon dioxide per megawatt hour. EPA administrator Gina McCarthy said that in order to meet the standard new coal plants would have to capture and store 20-40% of the carbon they produce. Coal advocates are likely to challenge the new rules. But it’s possible no coal plants will be built even if the proposed rules aren’t implemented because it’s already cheaper to produce energy with natural gas than with coal.

A Food and Agriculture Organization (FAO) report found that wasted food is a major contributor to climate change. The FAO says that about one-third of the food the world produces either never makes it to market or is thrown away by consumers. The FAO calculated that we produce the equivalent of 3.3 gigatons of carbon dioxide, consume 250 cubic kilometers of fresh water, and use 1.4 billion hectares of land every year growing food that ends up going to waste. A paper in Nature Climate Change estimated that aggressive cuts in carbon emissions could prevent as many as 3 million premature deaths a year by the year 2100. And a Bulletin of the American Meteorological Society report looked at 12 extreme weather events that occurred in 2012 and concluded that anthropogenic climate change was a contributing factor in half of them.

A paper in Proceedings of the National Academy of Sciences found that methane leakage rates from new shale-gas wells in the US is lower than had previously been estimated. The study also found that “green completion” techniques for capturing gas lost during well completion—which the EPA will require gas producers to use starting in 2015—are fairly effective in minimizing certain types of leaks. Washington Post reporter Brad Plumer wrote that if leakage rates are low, then shale-gas fracking may contribute less to climate change than burning coal does. But he also noted that the study looked only at the newest shale-gas wells and that it didn’t take into account leaks from pipelines or processing facilities. He also pointed out that if natural gas slows the development of solar or wind power, it will ultimately mean higher carbon emissions.

The X Prize Foundation announced $2 million in prize money for the development of sensors that can measure ocean acidity cheaply and accurately. As the amount of carbon dioxide in the atmosphere rises, more carbon dioxide dissolves in seawater. That raises the acidity of the oceans, with potentially huge effects on the health of marine ecosystems.

While ocean acidification is well documented in a few temperate ocean waters, little is known in high latitudes, coastal areas and the deep sea. and most current pH sensor technologies are too costly, imprecise, or unstable to allow for sufficient knowledge on the state of ocean acidification.

Right now pH sensors can cost $5,000 apiece and need frequent recalibration. University of North Carolina marine biologist John Bruno said that “Having a cheap, simple device that you can purchase commercially—not build—would revolutionize the science of ocean acidification.”

In The New York Times, University of Maryland geography professor Erle Ellis questioned the idea that the human population is close to the limits of what the planet can support. Ellis wrote that the planet probably couldn’t support more than 100 million hunter-gatherers, but the continuing development of agriculture has vastly expanded the number of human beings who can live on Earth. He argued that the human-carrying capacity of the planet is not a fixed limit, but grows as our social systems and technologies become more sophisticated. In a follow-up post, Ellis wrote that while large populations place greater demands on the environment, they also support more robust societies with greater technological capabilities. Robert Walker, President of The Population Institute, responded that it would be dangerous hubris to assume we can continue to survive on the planet as the population grows. “Past performance,” Walker wrote, “does not guarantee future results.”

According to a declassified 2009 US Department of Defense response plan, a flu pandemic could infect as many as 90 million people and kill as many 2 million people in the US alone. The Defense Department plan assumed that a vaccine for a novel flu strain would take 4-6 months to develop and that it would take substantially longer to produce a vaccine in large enough quantities to meet demand. And the plan warned that since the impact of a pandemic wouldn’t be limited to just one area, it would be more like “global war than an isolated disaster such as a hurricane, earthquake, or act of terrorism.”

The US Centers for Disease Control (CDC) issued a report assessing the threat posed by antibiotic-resistant organisms. The CDC estimated that more than 2 million illnesses in the US are caused each year by antibiotic-resistant bacteria and fungi. Those 2 million illnesses directly account for at least 23,000 deaths every year. The report blames the proliferation of antibiotic-resistant organisms in part on the overuse of antibiotics. CDC Director Thomas Frieden said that “about half of all the antibiotics used among people in the United States are either unnecessary or inappropriate.” The report also expressed concern about the use of antibiotics to promote growth in livestock. “If we are not careful, we will soon be in a post-antibiotic era,” Frieden said. “And for some patients and some microbes, we are already there.”

Eric Schlosser reported in a new book that the US came close to a major nuclear accident in 1961 when a B-52 bomber broke up in flight over Goldsboro, North Carolina and accidentally released two 4 megaton bombs. Schlosser obtained a recently declassified report that shows that all but one of the failsafe mechanisms on one of the bombs failed. If the bomb had gone off, the explosion would have been roughly 250 times more powerful than the one that destroyed Hiroshima. Schlosser said that there were at least 700 “significant” accidents involving nuclear weapons between 1950 and 1968 alone. In The Bulletin of the Atomic Scientists, Benoit Pelopidas wrote that it’s unrealistic to expect that no country or non-state actor will use nuclear weapons if we continue to have them.

Global Catastrophic Risk Institute Executive Director Seth Baum argued that the most important issue at stake in the Syrian civil war is actually the relationship between the US and Russia. Although more than 100,000 people have already died in the Syrian conflict, the consequences of a nuclear war between the US and Russia—which could kill billions or even mean the end of human civilization—would be orders of magnitude more tragic. Satellite imagery of the Yongbyon nuclear facility suggests that North Korea is restarting its five-megawatt gas-graphite reactor. The reactor is capable of producing roughly six kilograms of plutonium a year—enough for one or two nuclear weapons. Recently-elected Iranian president Hassan Rouhani told the UN General Assembly that Iran was ready to engage in talks about its nuclear program and that “nuclear weapons and other weapons of mass destruction have no place in Iran’s security or defense doctrine.” Patrick Clawson wrote in Foreign Policy that there are signs that Iranian Supreme Leader Ali Khamenei may be willing to consider a nuclear deal with the US.

NASA says that Voyager 1, the probe launched in 1977 to explore the outer solar system, has become the first man-made object to reach interstellar space. Indirect measurements of Voyager’s plasma environment indicate the spacecraft crossed the heliopause into interstellar space in August 2012. Wired reports that NASA has almost run out of plutonium-238, which is the primary fuel space missions like Voyager’s. Because plutonium-238 decays relatively quickly, it is practically non-existent on Earth in nature. Most of the world’s plutonium-238—which can’t be readily used in weapons—was produced during the Cold War as a byproduct of making plutonium-239 for nuclear bombs. NASA recently began experimenting on a small scale with new processes for producing plutonium-238.

A paper in Astrobiology estimated that as the Sun heats up the Earth will become uninhabitable some time in the next 1.75 to 3.25 billion years. The paper found that the habitable zone around the Sun—the region of the solar system which is neither too hot or too cold for liquid water to exist on a planet’s surface—is moving outwards at a rate of about a tenth of the distance from the Earth to the Sun every billion years. Andrew Rushby, who led the study, stressed that the slow heating of the Sun is unrelated to the rapid warming caused the human emission of carbon dioxide. And Lawrence Rifkin argued in Scientific American that we need to do more to ensure the survival of intelligent life on Earth. “We accept health insurance, car insurance, property insurance, life insurance, disability insurance, and dental insurance as societally appropriate and often worthwhile,” he wrote. “Let’s add existence insurance to the mix.”

This news summary was put together in collaboration with and is cross-posted at Anthropocene. Thanks to Seth Baum, Kaitlin Butler, and Grant Wilson for help compiling the news.

For last month’s news summary, please see GCR News Summary August 2013.

You can help us compile future news posts by putting any GCR news you see in the comment thread of this blog post, or send it via email to Grant Wilson (grant [at] gcrinstitute.org).