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U.S. GHG Emissions at Lowest Level in 20 Years

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U.S. greenhouse gas emissions declined 3.4 percent in 2012 from 2011, the Environmental Protection Agency announced Tuesday. Those emissions are down 10 percent from what they were in 2005, the EPA said, and are at their lowest levels since 1994.

Most of the decline came from reductions in energy consumption, increased fuel efficiency of cars and other types of transportation, and a shift to natural gas from coal in fueling power plants, the EPA said in a statement.

U.S. greenhouse gas emissions per year since 1990, broken down by type of gas.
Click image to enlarge. Credit: EPA

Whether the decline in emissions in the past few years is on  track to reach the pledge by the U.S. to reduce emissions by 17 percent compared to 2005 levels by 2020 is unclear.

“The decline that has been occurring the last few years could signal that emissions are turning downwards, however, they could also be the result of short-term fluctuations,” said climate scientist Bill Hare, CEO and managing director of Climate Analytics, a non-profit focused on climate research. (Hare’s group has said that pledge of 17 percent by the U.S. isn’t enough to reach the emissions reductions needed globally to avoid the worst effects of climate change.)

Carbon dioxide accounted for more than 80 percent of the greenhouse gas emissions, methane for nearly 9 percent, nitrous oxide for just more than 6 percent and other gases for smaller percentages. Most of the carbon dioxide came from the combustion of fossil fuels like coal and natural gas, while methane came mostly from livestock, decomposition of waste in landfills and natural gas systems.

A recent study found that methane emitted to the atmosphere through leaks in drilling systems were underestimated by the EPA. On a molecule-by-molecule basis, methane is a more potent greenhouse gas than carbon dioxide, but carbon dioxide is much more abundant in the atmosphere and is therefore the focus of most climate change mitigation efforts. Carbon dioxide passed the symbolic threshold of a concentration in the atmosphere of 400 parts per million for the first time last year. This year, it could surpass that mark for more than a month.

Electricity generation is the leading source of emissions in the U.S., with transportation coming in second.

The EPA has been compiling its Inventory of U.S. Greenhouse Gas Emissions and Sinks since 1990, and reports its findings to the Secretariat of the United Nations Framework Convention on Climate Change, as is required by countries who signed on to the convention. Since 1990, U.S. emissions have increased by 4.7 percent.

A Climate Central analysis of the American energy economy shows that the 10 percent reduction in annual carbon emissions in the U.S. since 2005 is unlikely to continue in the years ahead without major departures from the ways energy is currently produced and used.
Click image to enlarge. Credit: Climate Central

Greenhouse gases accumulating in the Earth’s atmosphere are the main driving force behind global warming.

Under President Barack Obama’s Climate Action Plan, the EPA has been directed to limit the greenhouse gas emissions from manmade sources, including new and existing coal-fired power plants.

Despite recent declines in emissions in the U.S. and in Europe, global emissions are still on the rise, largely because of developing economies like China’s, which are being powered by burning cheap, dirty fuels like coal. In the last part of its most recent assessment, the Intergovernmental Panel on Climate Change found that over the decade from 2000-2010 emissions reached their highest point in human history and rose at 2.2 percent per year compared with 0.4 percent per year in the previous three decades.

In order to keep warming under the 2°C (3.6°F) threshold agreed on by the world’s governments at a 2009 meeting in Copenhagen, global emissions will have to decline by 40 to 70 percent by 2050, the IPCC said in the most recent portion of its report, released Sunday.

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By Dave (Basking Ridge, NJ 07920)
on April 16th, 2014

With reference to the EPA bar graph, the claim of a net reduction that is reported here refers to all GHG’s. To my eye, according to the bar graph, none of the EPA reported emission amounts for methane, nitrous and the halogen compounds (the red, green and black bits, respectively) seem to have changed much, if at all, since 1990. Yet the natural gas boom is recent and has most definitely created a new and significant source of methane emissions due to leakage. So did the US livestock herd coincidentally decline just enough to precisely offset the recent rise in methane emissions due to the greatly expanded natural gas operations? Or is it a data entry error of some kind?

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By athompson
on April 17th, 2014

Hi Dave, the net reduction of 10 percent they’re talking about is from 2005. You’re right that they’re not much changed since 1990 when you look at the net change.

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By Miner49er (Glenview IL 60025)
on April 17th, 2014

GHG emissions are lower. Hooray! Are our lives better than 20 years ago? Because decreased employment and living standards are the cause of lower emissions. Fossil fuels are the stuff of which wealth is made. Less fossil fuels use—less wealth creation.

Human carbon dioxide emissions are only 3% of total CO2 emissions. CO2 does not materially affect climate. CO2 is absorbed by the oceans where it is efficiently converted to carbonate rocks like limestone (CaCO3). It remains in that form for tens of millions of years. There is no need to expend effort of money to capture and sequester CO2, because nature already does a good job for free.

All the known fossil fuels resources are insufficient to cause global warming. We can use all the fossil fuels we want for the benefit of humanity. Most fossil fuels that ever existed burned up through natural forces, so why aren’t we already toast? (and so will the rest, unless we use them to our benefit.)

The climate may (or not) be warming, but not because of carbon dioxide. We are, after all, in an interglacial period. Ice ages are more the norm than the exception on Earth. Warming is to be expected, when emerging from an ice age that just ended in the late 19th century. Thank heavens! Further warming will make our lives better.

The notion of “ocean acidification” because of ambient CO2 is a pure fabrication. The oceans are strongly alkaline, and have extremely high buffering capacity. All the known fossil fuels resources are not sufficient to acidify the seas. (Local acidification can result from other causes.)

The estimated cost of limiting carbon dioxide emissions is $65 trillion. The estimated cumulative savings of mankind is only $150 trillion. The estimated indebtedness of the United States is $17 trillion. The estimated unfunded obligations of the United States is $100 trillion. The estimated debt and unfunded obligations of the rest of the OECD is also $100 trillion. So we can’t afford to expend $65 trillion in a faint hope that it might delay global warming for a few weeks. We have more pressing problems to attend to, which will command our full attention soon.

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By Dave (Basking Ridge, NJ 07920)
on April 18th, 2014

That’s a pretty tired laundry list of ageing denier comments – all of which are either technically incorrect or distortions and all of which are also clearly and generally designed to mislead people into thinking there’s no problem.

To pick just one to start with, did you know for instance that uplift weathering has frequently been cited, and is generally regarded by paleoclimatologists as the cause of the last great ice age, which is called the Quaternary ice age or the current one?

Another one….  Yes, the current ice age. We are in an ice age now. (The so-called little ice age you apparently referred to was not actually an ice age.) An ice age is defined as a long period during which there is a persistent and significant amounts of permanent ice. So no, we haven’t just emerged from an ice age as you also claim. We are in the Quaternary ice age and that started about 2.6 million years ago.

Ocean acidification?  Also generally wrong there – but correct that the oceans are alkaline – although not very alkaline as you state. The pH is dropping a little due to enhanced CO2 absorption – that’s the acidification part of it. But the key problem to do with this is that the carbonate alkalinity is declining and that stresses a lot of marine life. You can ask an expert aquarist about that issue too because it is a known and highly well characterized problem that can occur in large indoor aquariums where ambient CO2 levels are often elevated.

What else… Or yes – you need to study up on the difference between the fast and slow carbon cycles. Yes, nature is cycling huge quantities of CO2 through respiration and photosynthesis. That’s the short cycle. But it is cycled and by definition pretty much balanced. Anthropogenic emissions are not balanced as you state by rock weathering or indeed any natural process. Rock weathering is part of the slow carbon cycle and it takes thousands of years to reduce CO2 levels. So in a nutshell, that’s why MEASURED atmospheric CO2 concentrations are rising so rapidly.

And yes, the planet is warming and the climate is generally changing in many places and no for many people and for oh so many reasons, that is not good news at all. All sorts of change indicators aside from global mean temperature, like sea level rise etc., are tracked and reported - in case you hadn’t heard.

Wealth creation from fossil fuels? Sure, for some – in the short term. Maybe you too? But future generations won’t feel very rich at all because they will bear the brunt of the worst of the climate change.

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By Dave (Basking Ridge, NJ 07920)
on April 17th, 2014

Thanks Andrea. Yes it is all very curious.

On this EPA web page:
The EPA claim: “Methane (CH4) emissions in the United States decreased by almost 11% between 1990 and 2012. During this time period, emissions increased from sources associated with agricultural activities, while emissions decreased from sources associated with the exploration and production of natural gas and petroleum products.”

On the face of it, 11% net reduction sounds positive, like some progress is being made. But it is unconvincing. This is for two reasons.

1. It is generally known that there is actually no hard data available for net US methane emissions in that at least the EPA ‘data’ with particular respect to natural gas is only based on estimates derived from the industry itself.

2. The massive boom in natural gas production has created widespread and significant new sources of methane leakage in the US. A logical expectation would therefore be to see net methane emissions significantly spike up because of that. By exactly how much we don’t yet know because it has not been comprehensibly measured. But it should be a noticeable up tick of some visible degree on a graph of measured emissions.

The EPA instead categorically state that net methane emissions have been steadily trending down, despite a growth in methane emissions from agriculture.

To re-emphasize, there is currently no comprehensive database for measured US net methane emissions which of course also includes leakage from fracking operations and vastly expanded production. There is an ongoing controversy over what might be the associated net rate of methane leakage because methane is such a powerful greenhouse gas and industry estimates are so low. The EPA methane leak rate estimate is based on industry estimates (1.4% of production) and is the lowest of all the numbers I have seen discussed by a range of expert sources.  The implication is therefore that in the absence of complete data, a more realistic, or likely lower error official estimate would be something that is higher than the lowest available estimate of 1.4%.  Clearly, for all we know the current EPA reported net US GHG emissions and emission trends could therefore also quite feasibly be substantially in error. This is clear cause for concern.

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