The Big Business of Global Warming

The pharmaceutical giant Bayer has made a remarkable — and lucrative — discovery. Allergies are on the rise. The company’s eye-and-nose ointment Bepanthen, already good for more than $200 million in annual sales, could soon be in even higher demand.

Bayer mentions this in its annual response to the watchdog CDP, formerly the Carbon Disclosure Project, which surveys the greenhouse-gas emissions of the world’s largest corporations. The CDP celebrates companies that cut carbon, of course, but also celebrates brutal honesty, awarding prizes and A rankings to those that give a true and full accounting of how climate change could affect their bottom lines. Bayer is a winner on both counts. Though still high, its emissions are down nearly 40% from 1990 levels. And the company is transparent about what it believes a warming world will bring.

One of Bayer’s latest products is “a new generation of mosquito net,” the LifeNet. It also has two advanced bug sprays in the pipeline. These will be lucrative because mosquitoes and the disease they carry are expected to thrive in a warmer world, leaving another 40 million to 60 million people at risk of malaria in Africa alone. “In light of an expected climate-change-related increase of malaria incidents in further regions of the world (e.g., Northern Europe), we expect a growing demand for Bayer mosquito nets,” the company writes.

For agriculture, the effects of climate change — “water shortages, heat, excessive rainfall” — will be devastating. But Bayer’s insecticide Confidor and its expanding line of genetically modified rice and cereal plants could profitably take out some of the sting. Even a future of superstorms could be a boon. “One example,” writes Bayer, “is the provision of high-performance polycarbonate materials for the construction of exposed buildings, leading to superior stability in the case of storms or other extreme weather events.” For existing structures, the company recommends its spray-on product Baytec, which leaves a thick coating of weatherproof polyurethane.

Bayer is not alone in seeing opportunities in a hotter planet. In Australia’s climate-stressed bread belt, the Murray-Darling basin, and its analog in the American West, the Colorado River basin, hedge funds have bought up millions of gallons worth of water rights. Other funds, convinced that commodity prices can only keep rising, are part of a new scramble for Africa in which as many as 100,000 sq. mi. of farmland — an area larger than the U.K. — have been leased or purchased by foreign investors. Meanwhile, at least two of Manhattan’s most storied investment banks have played farmer in Ukraine, where milder temperatures heighten the appeal of some of the richest soil in the world.

In the Netherlands, the stock of the seawall-building company Arcadis jumped by 6% the moment New York City — a potential client — was struck by Hurricane Sandy. Up in the melting Arctic, ship traffic has risen 20-fold in three years over the top of Russia on the Northern Sea Route. And receding sea ice puts an even greater prize within reach: oil. Royal Dutch Shell, which in 2008 paid a record $2.1 billion for leases in Alaska’s untapped Chukchi Sea, has told investors that the high north will someday be its No. 1 source of crude. Even in Greenland, the Danish territory synonymous with the slow-moving disaster that is climate change, people have found something to celebrate. Petroleum and precious-metal deposits made more accessible by the melting ice are so vast that native Greenlanders recently voted to leave Denmark and its subsidies behind. They will gradually drill their way to independence. The world will gain a new country even as others sink beneath rising seas.

Americans often frame climate change as a tragedy of the commons: we all pursue our selfish lives, we all emit, and together we all will someday pay. But this is a dangerous way to understand the future and our responsibilities to it. That some are planning to get rich from the warming world only underscores the reality of climate change: its impacts, though mostly bad for most people in most places, are deeply uneven.

It happens that those largely responsible for the historic emissions that got us here — wealthy North Americans and Europeans — are the most likely to stay relatively prosperous, because we have our northerly geographies and we have enough money in our wallets for, say, high-performance polycarbonate building materials. It happens that those least responsible for historic emissions, the equatorial and the poor, are the most likely to see the worst impacts, likely to get poorer faster. This unevenness suggests that self-interest, however rational, may never be enough to jump-start real climate action in the wealthy countries where it’s most needed. It’s hard to scare people into cutting emissions if they’re not actually all that scared.

There’s nothing wrong with selling mosquito nets, and there’s nothing wrong with buying them. But there’s something wrong if we ignore the true ethical stakes as an ever more imbalanced world keeps lurching ahead, blithely thinking, “At least we’re all in this together.”

What Causes Global Warming?

Global warming has surfaced as a major environmental issue, especially over the past few decades. There has been a lot of hue and cry about global warming, and its impact on the climate, ever since the idea was first put forth. Even though there is no dearth of books or articles on the Internet, the layman still seems unaware of the basic causes of global warming.

Causes of Global Warming

Global warming is basically a change in the climatic conditions of the Earth, brought about by a considerable rise in the near-surface temperature of the planet. A number of factors have been contributing to this rise in the average global temperature - either directly or indirectly, right from the time the planet came into existence. It is the alarming rate at which the temperature has been rising over the last few decades that has put the scientific fraternity on its toes, and the desperate measures to find out what is causing the global temperature to rise at this rate, hints at this very fact.

Global warming, and the resulting climate change, can be caused by natural as well as man-made factors (anthropogenic factors, to be precise). The natural factors causing this sudden warming of the planet include the greenhouse effect, solar activity, volcanic emissions, orbital forcing (slow tilting of the Earth's axis), etc. The anthropogenic causes, on the other hand, include various human activities - right from breathing (respiration), to the use of vehicles and various industrial processes, which add to the greenhouse effect and cause the Earth to become warm.

Greenhouse Effect

The greenhouse effect is said to be the most crucial factor contributing to global warming. It refers to the process wherein the radiations coming from the Sun are trapped by the greenhouse gases within the atmosphere of the Earth, which in turn causes the temperature near the Earth's surface to soar. The greenhouse gases in question here, include carbon dioxide, carbon monoxide, methane, chlorofluorocarbons (CFCs), water vapor, etc. It is believed that the greenhouse effect has increased the Earth's temperature by somewhere around 24 percent, with carbon dioxide contributing to about 12 percent of the greenhouse effect, water vapor contributing around 36 percent, methane 5 to 10 percent, and Ozone making around 3 to 7 percent to the same.

Solar Variation

The changes in the amount of radiant energy emitted by the Sun, i.e. solar variation, is said to be yet another reason of global warming. This solar variation has been correlated with the changes in the Earth's climate and temperature. The solar variation theory states that the amount of solar radiation has been increasing with time. If the proponents of this theory are to be believed, the Sun has been gaining strength, and is at its strongest since the last sixty odd years. And thus, it is believed that the Sun may now be acting as a cause of global warming.

Sunspots

Sunspots are also said to be a cause or catalyst for global warming. Recent reports suggest that the number of sunspots in an area directly affects the amount of time taken by that region to cool down. The Sun is the main source of energy to the Earth. The Earth absorbs about 70 percent of the solar flux, which - in turn increases the temperature of the Earth's atmosphere, land and oceans.

Human Activities

It isn't quite a coincidence that global warming and industrialization seem to go hand in hand, and that becomes obvious as you compare the industrialization and temperature rise trends over the last few decades. Even scientists acknowledge that rapid industrialization, wherein we have opted for quite a few shortcuts, has contributed to the increase of global warming today. Humans had started contributing to global warming some 8000 years ago with the start of agriculture, wherein deforestation to clear land for farming resulted in a significant rise in the amount of carbon dioxide in the atmosphere. A prominent greenhouse gas, methane is released in the atmosphere as a part of the digestive process in cattle and other ruminating animals.

Scientists are of the opinion that bad practices in industries result in release of various greenhouse gases which eventually trap the Sun's radiations in the atmosphere, and contribute to global warming. Though the use of household appliances which release chlorofluorocarbons (CFCs) in the atmosphere has come down now, it was at its peak in the 90s and caused irreversible damage to the atmosphere. Other than cattle, methane also exists in plenty beneath the Earth's crust, and the release of methane during mining indirectly contributes to rising temperature on the planet. Other than deforestation, humankind has also contributed to global warming by using fossil fuels, which emit carbon dioxide and other such harmful gases.

While all the natural factors do come into play when it comes to global warming, one has to understand that they are necessary in maintaining the right balance on the Earth. Had it not been for all these natural occurrences, the entire planet would have had been a cold desert resembling the continent of Antarctica. In fact, some scientists are of the opinion that human life would have been impossible on the planet in the absence of greenhouse effect (human activities excluded), because the average temperature of the planet would be around 27°C in that case.

Global warming continues and won’t be stopped by wishful thinking

Global warming has continued rapidly in recent years, mostly accumulating in the oceans. Yet there remains a pervasive myth that it has somehow magically stopped.   Most recently displaying this confusion was Georgia Tech climate scientist Judith Curry, who testified about climate change before a U.S. Senate committee. Curry's testimony was riddled with mistakes and misleading arguments, the worst of which involved disputing that climate scientists are more confident in human - caused global warming than they were six years ago.   Curry based this argument in large part on the supposed global warming 'pause', which is itself a fictional creation. While the warming of average global surface temperatures has slowed (though not nearly as much as previously believed), the overall amount of heat accumulated by the global climate has not, with over 90 percent being absorbed by the oceans, and 30 percent of that in the deep oceans (below 700 meters) over the past 15 years.   A few days after her Senate testimony, Curry took to her blog to dispute these data, essentially arguing that the amount of heat absorbed by the oceans has also 'paused', which would then support her arguments. However, in evaluating the ocean heat content data and scientific literature, Curry made a number of mistakes.   First, she claimed that the only evidence of buildup of heat in the deep oceans comes from reanalysis products. A 'reanalysis' is a climate, ocean, or weather model simulation of the past that incorporates data from historical observations. However, in reality, the increase in deep ocean heat accumulation is a robust result also observed in data sets that do not include reanalysis.    Ocean temperature   In fact in a paper my colleagues and I published in 2012, we showed that according to the observational ocean temperature data compiled by the National Oceanographic Data Center, about 30 percent of global warming has gone into the deep oceans since the year 2000 – the same result as in subsequent studies using reanalysis data. On top of that, the new paper that Curry referenced in her blog post by scientists from the National Oceanic and Atmospheric Administration (NOAA) found that even more heat has built up in the deep oceans – over 40 percent of overall global warming since 2004.   So what caused Curry to claim that global and ocean warming had 'paused' since 2003? In her blog post, she tried to do science by eyeball. Scientists use statistics because our senses can introduce bias and deceive us. Instead, Curry looked at the following figure from the NOAA paper and decided it looked like ocean warming had stopped in 2003.   The NOAA scientists had actually statistically evaluated data, and found that between 2004 and 2011, the oceans (to a depth of 1,800 meters) had absorbed heat at a rate equivalent of 4.5 Hiroshima atomic bomb detonations per second, according to measurements from instruments on Argo buoys.   In addition to these direct ocean temperature measurements, we also know from satellite observations that the planet is accumulating heat owing to a global energy imbalance. Due to the increased greenhouse effect 'trapping' more heat, there's more incoming than outgoing energy at the top of the Earth's atmosphere. The laws of physics tell us that energy has to go somewhere, which pokes a giant hole in the global warming 'pause' wishful thinking.    Because they absorb over 90 percent of that energy, we fully expect the oceans to do exactly what they're doing – accumulate a whole lot of heat. If global warming were to 'pause', it would require an explanation of where the energy from the global imbalance measured by satellites is going.    A new study led by Kevin Trenberth notes that the amount of heat accumulating in the oceans and the rest of the global climate is generally consistent with the global energy imbalance measured by satellites. There's also the issue of sea level rise, whose main contributors are melting glaciers and ice sheets, and thermal expansion (water expanding as it warms).    Climate scientists   Climate scientists have been able to close the sea level 'budget' by accounting for the various factors that are causing average global sea levels to rise at the measured rate of about 3.2 millimeters per year since 1992 (when satellite altimeters were launched into space to truly measure global sea level). The warming oceans account for about 40 percent of that rate of sea level rise over the past two decades. If the oceans weren't continuing to accumulate heat, sea levels would not be rising nearly as fast.   Curry also makes the mistake of arguing that the rate of sea level rise during 1930–1950 was similar to that in recent years (most studies estimate that it was lower), which she implies tells us something about the current rise in ocean heat content. This argument is a non sequitur – the conclusion doesn't follow from the premise of the argument. Yes, global warming events have occurred naturally in the past, and sea level rose as a consequence, but that doesn't tell us anything about the causes of the current global warming. This argument is akin to seeing a dead body with a knife sticking out the back and arguing that it must have been a natural death because people have died naturally in the past.    The bottom line is that all available ocean heat content data show that the oceans and global climate continue to build up heat at a rapid pace, consistent with the global energy imbalance observed by satellites. In recent years, much of that heat has accumulated in the deep oceans. While the rate of increase of global surface temperatures in recent years has slowed in large part due to the more efficient heat transfer to the deep oceans, that can't last forever.   When that trend reverses (likely within the next decade,) we'll experience an acceleration of warming at the Earth's surface. Global warming has only slowed at the surface, not in the overall global climate, and only temporarily. Arguments to the contrary are based on wishful thinking and allowing one's biased senses to be deceived.    The problem is that we're wasting time hoping that the temporary slowing of rising surface temperatures means we no longer have to worry about global warming, when there's simply no evidence that's the case. The oceans have given us at the surface a temporary reprieve, and we continue to waste it by failing to take serious steps to address the underlying problem; a problem that wishful thinking can't solve.

Clouds Cast Doubt On Global Warming Predictions

The warming effect of human-induced greenhouse gases is a given, but to what extent can we predict its future influence? That is an issue on which science is making progress, but the answers are still far from exact, say researchers from the Hebrew University of Jerusalem, the US and Australia who have studied the issue and whose work which has just appeared in the journal Science. Indeed, one could say that the picture is a “cloudy” one, since the determination of the greenhouse gas effect involves multifaceted interactions with cloud cover.

To some extent, aerosols – particles that float in the air caused by dust or pollution, including greenhouse gases – counteract part of the harming effects of climate warming by increasing the amount of sunlight reflected from clouds back into space. However, the ways in which these aerosols affect climate through their interaction with clouds are complex and incompletely captured by climate models, say the researchers. As a result, the radiative forcing (that is, the disturbance to the earth’s “energy budget” from the sun) caused by human activities is highly uncertain, making it difficult to predict the extent of global warming.

And while advances have led to a more detailed understanding of aerosol-cloud interactions and their effects on climate, further progress is hampered by limited observational capabilities and coarse climate models, says Prof. Daniel Rosenfeld of the Fredy and Nadine Herrmann Institute of Earth Sciences at the Hebrew University of Jerusalem, author of the article in Science. Rosenfeld wrote this article in cooperation with Dr. Steven Sherwood of the University of New South Wales, Sydney, Dr. Robert Wood of the University of Washington, Seattle, and Dr. Leo Donner of the US National Oceanic and Atmospheric Administration. .

Their recent studies have revealed a much more complicated picture of aerosol-cloud interactions than considered previously. Depending on the meteorological circumstances, aerosols can have dramatic effects of either increasing or decreasing the cloud sun-deflecting effect, the researchers say. Furthermore, little is known about the unperturbed aerosol level that existed in the preindustrial era. This reference level is very important for estimating the radiative forcing from aerosols.

Also needing further clarification is the response of the cloud cover and organization to the loss of water by rainfall. Understanding of the formation of ice and its interactions with liquid droplets is even more limited, mainly due to poor ability to measure the ice-nucleating activity of aerosols and the subsequent ice-forming processes in clouds.

Explicit computer simulations of these processes even at the scale of a whole cloud or multi-cloud system, let alone that of the planet, require hundreds of hours on the most powerful computers available. Therefore, a sufficiently accurate simulation of these processes at a global scale is still impractical.

Recently, however, researchers have been able to create groundbreaking simulations in which models were formulated presenting simplified schemes of cloud-aerosol interactions, This approach offers the potential for model runs that resolve clouds on a global scale for time scales up to several years, but climate simulations on a scale of a century are still not feasible. The model is also too coarse to resolve many of the fundamental aerosol-cloud processes at the scales on which they actually occur. Improved observational tests are essential for validating the results of simulations and ensuring that modeling developments are on the right track, say the researchers.

While it is unfortunate that further progress on understanding aerosol-cloud interactions and their effects on climate is limited by inadequate observational tools and models, achieving the required improvement in observations and simulations is within technological reach, the researchers emphasize, provided that the financial resources are invested. The level of effort, they say, should match the socioeconomic importance of what the results could provide: lower uncertainty in measuring man-made climate forcing and better understanding and predictions of future impacts of aerosols on our weather and climate.

Global Warming First Caused by Ancient Farmers

Ancient farmers may be responsible for the warming up of the Earth by around 0.9 degree Celsius, which is as much as that has been caused in the past 150 years, a new study revealed.

The finding, by a new study, suggests that early agriculture was as powerful as the whole industrial revolution, says Feng He, lead author and a climate scientist at the University of Wisconsin, Madison.

The study, however, says that the "net warming" caused by early humans was only 0.73 degrees Celsius, thanks to a slight cooling due to more sunlight reflecting from cleared land.

The study says that while early cultures were "global warming turtles" that slowly raised temperatures by adding greenhouse gases such as carbon dioxide and methane to the planet's atmosphere over thousands of years, post-industrial revolution societies have "climate change rabbits".

They were responsible for temperatures rising about 0.85 degrees C between 1880 and 2012, according to the Intergovernmental Panel on Climate Change (IPCC).

Usually, 1850 is picked as the kickoff for global warming, but the study suggests human activities such as deforestation and agriculture could have shifted the climate earlier.

And ice cores suggest this is indeed the case: carbon dioxide and methane levels over the past 8,000 years do not follow their usual post-ice age trends. The gases go up as human population booms, instead of their usual decline.

Feng He and his co-authors estimated past global temperatures with climate models that calculated the effects of land-cover changes such as deforestation and irrigation.

They compared climate models of a human-free Earth to a planet crawling with hunter-gatherers and farmers. The researchers used estimates of past land-use from a past study that built a detailed model of land-use over time based on historical and archaeological data.

The study says that after the last ice age ended, carbon dioxide and methane levels should have dropped to about 245 parts per million (ppm) and 445 ppm without human influence on the planet.

Instead, carbon dioxide rose about 40 ppm, to 285 ppm, and methane jumped to 790 ppm, a 345 ppm rise, as early humans chopped down trees and irrigated rice fields.

"In terms of long-term climate change, the last several thousand years are unique because of this human factor in it," Feng He said. "It's almost like we're on a speeding train without a brake, but we are continually putting in the coal into the engine."

New NASA Satellite Would Observe Global Rainfall

Precipitation could finally be measured from space rather than the ground.

What's 39.3 feet long, weighs 8,598 pounds and can see raindrops from space?

NASA's new rain and snow satellite, which will launch from Japan in a month.

The satellite is called the Global Precipitation Measurement Core Observatory, or GPM, and is the first satellite to offer a near-global picture of rain and snowfall over the Earth.

"Rain and snowfall affect our daily lives in many ways. ... Extreme precipitation events like hurricanes, blizzards, floods, droughts and landslides have significant socioeconomic impacts," Steven Neeck, deputy associate director of the NASA Earth Science flight program, said at a media briefing held yesterday.

"GPM, through its core observatory and constellation of satellites, will dramatically improve our knowledge of global precipitation and our ability to forecast it and its consequences," he added.

Many developed countries such as the United States and much of Europe have ground-based instruments to detect and measure rain and snowfall.

But in much of the world -- over the oceans, in developing nations and near the poles -- measurements of precipitation are few and far between, or even nonexistent.

The GPM satellite has its own dual-frequency radar instrument to measure rainfall but will also use radar instruments on existing satellites (they include satellites from other countries as well) to gather information about global precipitation.

It also has a microwave imager that can see the precipitation in all layers of clouds.

Gail Skofronick Jackson, a GPM deputy project scientist at NASA's Goddard Space Flight Center, said the satellite will be able to see through clouds in three dimensions, like a CT scan, as well as all the way through the cloud, like an X-ray.

Prompt information could save lives

Once the satellite is launched in late February and completes a 60-day checkout period, the data it collects will be made available for public use every three hours. This could provide a lifesaving capability, NASA scientists said.

"Can you imagine if flood forecasting and landslide forecasting had estimates within three hours after data collection, every three hours, all day long? That means that the emergency planners can evacuate if necessary," Skofronick Jackson said.

Climate researchers will also be able to use the precipitation information gathered by the satellite, whose latitudinal range extends from 65 degrees north to 65 degrees south -- from far northern Alaska down to the Antarctic peninsula.

"Currently we have very little information from ground-based measurements over the interior continents like Canada, Siberia and especially over the high-latitude oceans," said Steve Nesbitt, an atmospheric scientist at the University of Illinois who will be using data from the satellite once it is launched.

"It's kind of like a black hole for precipitation."

Gaining access to rain and snowfall data in these far-flung locales will help researchers improve climate models, Nesbitt said. Polar researchers will finally be able to have data on how much it is snowing and where.

Data from the satellite may also help improve spring runoff forecasts in places like northern Canada, parts of the Alps and in the U.S. West, where snowmelt plays a key role in providing water for the rest of the year.

"It's true in the United States we have a pretty extensive distribution of snowfall measurements in the Rockies, but even with hundreds of stations, GPM is going to have such high resolution that we can really start to drill down into different areas that we haven't before," Nesbitt said.

Flood of new data for climate models

Christopher Williams, an atmospheric scientist at the University of Colorado, Boulder's Cooperative Institute for Research in Environmental Sciences, has been working with NASA researchers to improve how climate models represent rain processes.

So far he's used data from the Tropical Rainfall Measuring Mission (TRMM), a NASA satellite that launched in 1997. But TRMM only measures rain in the tropics. Now Williams will be able to work with modelers to globally improve how they represent rainfall.

He does this by comparing model runs with real-world measurements. If, for example, the model predicts heavy rainfall when it actually only drizzled, Williams works to help modelers tune the models and figure out what their algorithms might be missing.

The new precipitation satellite, a collaboration between the Japanese Aerospace Exploration Agency, known as JAXA, and NASA, has been a work in progress for more than a decade. Although its design life is just three years, it has enough fuel to last 12 or 13 years, and NASA officials hope it will work for at least five.

The GPM launch is scheduled for between 1:07 and 3:07 p.m. EST Feb. 27 from JAXA's Tanegashima Space Center in Japan.

Illinois' Nesbitt was in graduate school when TRMM, the first precipitation satellite, launched. Having watched its progress for most of his career, he sees the launch of GPM as a moment for celebration. Nesbitt is planning to have a party to watch the takeoff live.

Williams was also excited about the impending launch and said the buildup to it was "nerve-wracking." "We've been talking about this for years now, and it's finally a month way," he said. 

Why Is There More Methane in the Atmosphere?

Levels of the potent greenhouse gas continue to rise and scientists aren't sure where most of it is coming from, though likely suspects include fracking, increased coal mining in China and a melting Arctic.

 In 2006, the scientists who monitor methane, a greenhouse gas about 30 times more potent than carbon dioxide, thought that concentrations of the gas, which had sharply risen in the 1980s, had plateaued.

"If you look at the entire record from the beginning to 2006, it looks like a chemical system that is approaching steady state," said Edward Dlugokencky, an atmospheric chemist at the National Oceanic and Atmospheric Administration's Earth System Research Laboratory who monitors global methane emissions.

A puzzling aspect to this flattening of the methane trend was that, starting around 2000, China and other Asian countries were experiencing rapid development.

Typically, this would have resulted in increased methane emissions, Dlugokencky said.

"Chinese production of coal, which has methane emissions associated with it, had been increasing by about 7 percent per year since 2000, yet we see that methane is really flat in that period," he said. "So if there are increased anthropogenic emissions from increased fossil fuel use particularly in China, there has to be something that compensates for them."

The researcher hypothesized that methane emissions from wetlands, which are the biggest source of methane worldwide, were lower during that period, balancing out any increase from Asian development.

A mystery takes wing

As Dlugokencky and others write in a perspective paper published yesterday in the journal Science, accounting for the reasons behind trends in methane emissions is still an area of scientific uncertainty.

Since 2007, they report, methane has been on the rebound, with atmospheric concentrations growing quickly.

"There are a lot of puzzles as to exactly why it's growing," said Euan Nisbet, an earth scientist at the University of London who was the paper's lead author.

"Part of this article was trying to figure out the causes of the more recent growth, and there seem to be quite a lot of causes. And there's still some very big science problems as to what actually is going on," Nisbet added.

Scientists point to a few main reasons for the growth in methane over the past seven years. First, wet periods in the southern tropics have led to wetlands growing and lasting longer. That's one big source of methane.

Also, in 2007, methane emissions from the Arctic increased, probably because higher temperatures led to wetlands there releasing more of the gas.

A third reason for the increase in recent years is the growth in fossil-fuel-related emissions, Nisbet said.

If you can't measure it, can you reduce it?

"We've been using quite a lot more coal, especially in China, and more natural gas," he said. Both of those sources leak methane.

In the United States, researchers measuring methane leaks from natural gas have often come up with higher leak estimates than those of U.S. EPA, which uses a "bottom up" approach of multiplying a calculated emissions rate by the number of a certain type of source (ClimateWire, Nov. 26, 2013).

"Doing a bottom-up estimate is quite difficult," Nisbet said. "Because you are trying to calculate gas leaks, landfill leaks, you count up all the cows and you multiply by how much you think they are emitting. So it's a tough job."

One way to improve global methane measurements, the researchers said, is to increase the number of stations where methane is measured. In particular, tropical regions are lacking in measurements, and the Arctic could also benefit from additional measurements.

"The tropics are a very important region because so much is happening there," Dlugokencky said.

If methane emissions were better understood, policymakers could potentially reduce greenhouse gas emissions without too much effort, Nisbet added.

"You don't have to completely rearrange the entire world economy to [reduce methane emissions]. You've got to stop some gas leaks, you've got to stop some grass fires or stop landfill emissions. So methane is a very important target," Nisbet said.

"But we have to know where it is coming from. If we want to bring down the sources, we have to know where the sources are. And for that we need more measurements."