Study: Climate Change Probably Won’t Kill All of Us

A conveyor belt sits below excavated land at the Garzweiler open cast lignite mine. Photo: Krisztian Bocsi/Bloomberg via Getty Images

Due to a combination of prudence and morbid curiosity, a great deal of scholarly research (and journalism) about climate change has focused on the worst of all possible worlds. For scientists running climate-economic models, that nightmare scenario has a concrete definition: In 2011, such researchers established four baseline scenarios for the future of greenhouse gas emissions (ranging from the benign to the catastrophic) for the sake of facilitating comparable studies.

The most fearsome — and widely cited — of these baselines, known as “RCP8.5,” imagined a year 2100 in which an overpopulated, technologically underdeveloped humanity is digging up and burning every last piece of coal it can find. Thus, by the turn of the next century, coal — the most carbon-intensive major fuel source — would account for 94 percent of the world’s energy supply. In 2015, that figure was 28 percent.

This scenario, and other, less severe hypotheticals that also imagine a resurgence of coal use, have loomed large in both the academic and political debates over climate change. In its most recent report, the Intergovernmental Panel on Climate Change cited 210 scenarios that assumed humanity would move toward more carbon-intensive forms of energy in the coming decades.

But a new analysis from researchers at the University of British Columbia suggests that this assumption — and the nightmare scenarios that derive from it — merits less attention than it’s been given.

Their reasoning is simple. First and foremost, there probably isn’t enough extractable coal on the planet to make RCP8.5 possible, even if future humans tried to use that filthiest of fossil fuels for virtually all of their energy needs. Second, there’s little basis for thinking that we will become more reliant on carbon-intensive energy sources in the future. For decades, the ratio of greenhouse gas emissions to energy produced (i.e., the carbon intensity of energy) has been going down. And the growing prevalence of natural gas and renewable fuels strongly suggests this trend will continue.

The nightmare scenario looked considerably more plausible just a few years ago, when China’s consumption of coal was steadily rising. But precisely because that fuel is so dirty, anti-pollution political sentiment has pushed the Chinese government to move aggressively toward renewables, and many experts believe the nation’s coal consumption has already peaked.

There’s still no guarantee that we’ll be spared the worst of all possible climates. Even without a coal resurgence, there are plenty of other forces that could upend encouraging trends, including feedback from the warming we’ve already built in — like, for example, a surge of methane emissions from melting permafrost. Furthermore, there remains a lot that we don’t know about how the climate will evolve. One recent study found that aerosols, tiny atmospheric particles found in air pollution, may be suppressing global temperatures by as much a 1.1 degrees Celsius. If true, this would mean that reductions in greenhouse gas emissions would have a less significant effect on global temperatures than previously thought, as they would produce a concomitant decrease in the atmosphere aerosol content.

Nonetheless, there is some reason to think we’ve been overestimating the likelihood of total catastrophe. Which isn’t to say that humanity doesn’t need to radically ramp up its efforts to combat climate change. In fact, this new research suggests that international efforts aren’t aggressive enough: If the baseline trend points toward a greater degree of “passive decarbonization” — reductions in greenhouse emissions through the evolution of energy markets — then governments have been overestimating the economic costs of setting even more stringent caps on carbon emissions.

And make no mistake: Even if near-term planetary extinction looks unlikely, humanity still has a moral and practical obligation to cut emissions as quickly as possible. The worst-case scenario may be less likely than we thought. But very, very bad scenarios remain almost certain. Climate change is already devastating and destabilizingwhole regions of the Earth and increasing the intensity and frequency of extreme weather.


Methane from Indian livestock adds to global warming

A zebu bull

A zebu bull Copyright: B. Greene, Wikimedia – Creative Commons Attribution 2.0 Generic

By: S. Singh

NEW DELHI Methane produced by India’s livestock population, considered the world’s largest, can significantly raise global temperatures, says a new study designed to help predict climate change linked to greenhouse gas (GhG) emissions from farm animals.

Results of the study carried out by the Indian Institute of Technology Delhi and the Deenbandhu Chhotu Ram University of Science and Technology, Murthal and published this month (January) in Ecotoxicology and Environmental Safety show that the Indian livestock emitted 15.3 million tonnes of methane in 2012. Globally, the livestock sector is a major source of anthropogenic (human-induced causes) methane emission with annual global contribution of 14.5 per cent.

“The impact on climate change is global in result, so the negative impact due to livestock emission is not restricted to India,”

Shilpi Kumari, author

Shilpi Kumari, corresponding author of the study, tells SciDev.Net that the livestock sector in India has the potential to cause surface temperatures to surge up to 0.69 millikelvin over 20-year time period which is roughly 14 per cent of the total increase caused by the global livestock sector.

“The impact on climate change is global in result, so the negative impact due to livestock emission is not restricted to India,” Kumari says. India, with a livestock population of more than 500 million head, leads livestock- dominant countries such as Brazil, China and the US. Cattle and buffalo were found by the study to be the major sources of methane among India’s livestock accounting for 98 per cent.

Better livestock rearing practices such as using suitable feed types and improving livestock productivity can achieve reduction in methane emission, says Kumari.

Growth of livestock population is the key factor influencing levels of atmospheric methane, Kumari says. However, environmental risk management through improved livestock productivity, population stabilisation, better feed and manure use could reduce methane levels.

“In India, keeping livestock is mostly confined to the rural areas where opting for modern technologies is not possible due to dearth of money,” Kumari says.

According to Gufran Beig project director, System of Air Quality and Weather Forecasting and Research at the Indian Institute of Tropical Meteorology, New Delhi, the study is “noteworthy” given the background of climate change and because it highlights the need for technological solutions.

“Methane has a warming potential 20 times higher than carbon dioxide. In the Indian context, methane emissions are worrying because two major sources, livestock and paddy fields, are rapidly growing,” says Beig, “Both sources are connected to the Indian economy and food security.”

Cattle Grazing on Federal Public Lands Contributes to Global Climate Change

by Mike Hudak

10 November 2008

Revision dates: 5 February 2013, 21 July 2015,
7 February 2017, 10 July 2017




In this essay I will estimate the annual contribution to atmospheric green-house gases from methane (CH4) that results from enteric fermentation1 in cattle that graze on U.S. federal public lands. I’ll also compare the CH4 con-tribution of public lands cattle to that of several other sources and sinks of CH4, including emission of CH4 due to oil and gas production on federal lands.
The amount by which the public lands contribution to atmospheric CH4would change as a result of cattle removal is a more complex matter than are the above-mentioned topics. In the absence of ranching operations, the re-covery of native flora and fauna would provide many new sources and sinks of atmospheric CH4. Although a detailed greenhouse gas analysis of such re-covered ecosystems is beyond the scope of this essay, I will note a few factors that such an analysis should include.


Calculation of Cattle-Emitted CH4 Based on Amount of Forage Consumed


Based on the measurement that a typical grass-fed cow emits 600–700 liters (L) of CH4 per day,2 the mass of this gas annually produced by cattle that graze on 250 million acres of federal public lands managed by the U.S. Forest Service and the Bureau of Land Management (BLM) can be estimated.3 In the interest of producing a conservative estimate, I will perform the calculation using the lower limit (i.e., 600 L) of a cow’s daily CH4 production.
The BLM4 and U.S. Forest Service5 report annual forage utilization from their lands by cattle of 7,920,576 and 6,380,872 animal unit months (AUMs) respectively, with the combined forage utilization being 14,301,448 AUMs.
As each AUM represents 31 days of a cow’s forage consumption, it likewise represents 31 days of that animal’s CH4 production, and therefore each AUM consumed produces 18,600 L of CH4.6
Based on the total number of AUMs used per year and the mass of CH4emitted per AUM, the annual volume of CH4 produced by public lands cattle is equal to 266,006,932,800 L.7 Since 1,000 L are equivalent in volume to 1 cubic meter (m3), public lands cattle produce 266,006,932 m3 of CH4 per year.
Based on the density of CH4 being 0.68 kg/m3, under assumed conditions of 1.013 bar (one atmosphere) and 15°C (59°F),8 the mass of this volume is 180,884,714.3 kg.9
Gases, such as CH4, contribute to global warming. The relative ability of CH4 to trap heat in the global climate system over a given time frame (com-pared to CO2) is expressed by CH4’s “global warming potential” (GWP).10Internationally accepted values for CH4’s GWP (with climate-carbon feedback) are “34” over a 100-year interval (GWP100) and “86” over a 20-year interval (GWP20).11 Stated otherwise, over a 20-year interval, a given mass of CH4would have the same effect in the global climate system as a mass of CO2 that is 86 times greater than that mass of CH4.12
Authors of climate-related articles have often chosen to consider CH4’s impact over a 100-year period. But in 2013, the IPCC noted that “there is no scientific argument for selecting 100 years compared with other choices.”13Moreover, the IPCC found that at the 20-year timescale, total global emissions of CH4 are equivalent to over 80% of global CO2 emissions.14 In that light, Howarth (2014) argued for focusing on the 20-year rather than the 100-year period based on “the urgent need to reduce methane emissions over the coming 15–35 years.”15
Applying GWP20 for CH4 of 86, the environmental impact of the mass of CH4 produced by public lands cattle is equivalent to 15,556,085,430.14 kg of CO2 (over a 20-year interval).16


Sources of Emissions and Sequestrations of Greenhouse Gases Equivalent to the CH4 Emitted by Cattle on Public Lands


The U.S. Environmental Protection Agency’s online Greenhouse Gas Equivalencies Calculator17 reports that the 15,556,085,430.14 kg of CO2-equivalent annually cow-emitted CH4 is equivalent to any of the following:


•  Annual greenhouse gas emissions from 3,288,813 passenger vehicles
•  Carbon (C) sequestered by 398,873,984 tree seedlings grown for 10 years
•  C annually sequestered by 14,675,552 acres of U.S. forests
•  C annually sequestered by 123,992 acres of forest preserved from conversion to cropland.


CO2 emissions from


•  1,750,431,574 gallons of gasoline consumed
•  36,176,942 barrels of oil consumed
•  205,931 tanker trucks’ worth of gasoline
•  the electricity use of 2,297,118 homes for one year
•  the energy use of 1,642,670 homes for one year
•  burning 16,602,012,166 pounds of coal
•  burning 82,842 railcars’ worth of coal
•  648,170,225 propane cylinders used for home barbecues
•  4.5 coal-fired power plants for one year.


CH4 Emissions from Cattle Viewed in the Context of CH4 Wasted During Gas and Oil Production


In addition to providing forage for livestock, federal lands produce sig-nificant quantities of oil and natural gas. In FY2014 these lands produced 148,802.95 thousand barrels of oil and 2,499,845.86 million cubic feet of natural gas.18
In the course of their installation and operation, these oil and gas wells waste natural gas (primarily consisting of CH4) through venting, flaring, and leaks. An Environmental Defense Fund report dated September 201519 cites an analysis by ICF International20 that estimates these losses for 2013. Based on a graphic produced from the ICF report,21 I compute that these lands accounted for CH4 emissions of approximately 47.2 billion ft3, or equivalently 1,336,555 m3. The 266,006,932 m3 year-1 of CH4 emitted by the cattle on these lands therefore amounts to 19.9% of the CH4 emissions from current oil and gas production.22
On 15 November 2016, the BLM issued a rule that the agency has stated would annually reduce by between 175,000 and 180,000 tons the CH4 that is wasted during the construction and operation of gas and oil wells on public and tribal lands.23 Assuming the less optimistic, lower, value of the range, the CH4annually emitted by the public lands cattle represents 113.9% of this antici-pated annual reduction.24


Would Removing Cattle from Public Lands Reduce the Lands’ Greenhouse Gas Contribution?


Having determined the quantity of CH4 produced by cattle that graze on public lands, one might ask whether removing these cattle would reduce the greenhouse gas contribution of these public lands by that amount. Although the answer to that question is beyond the scope of this essay, I will indicate a few of the factors that must be considered in seeking the answer.
Removing cattle from public lands would allow several ecosystem com-ponents to begin their recovery from more than a century of harmful impacts. In particular, vegetation that had been consumed by cattle would now be available for wildlife. Consequently, we would expect wildlife populations to increase. And among that wildlife would be native ruminant mammals, such as elk, pronghorn and deer, which, like cattle, emit CH4 as a by-product of their digestion. But such animals produce the gas in much smaller quantities than cattle. For example, an individual deer produces on average only 31.5 grams of CH4 per day25—approximately 7.7% of the amount produced by a cow.26
Perhaps the removal of ranching from federal public lands would reduce much of the public opposition to restoration of predator populations, especially wolves. If predator populations were to increase, they would tend to limit the populations of native ungulate CH4 producers.27
Following the exclusion of cattle, research shows that land-based sources of atmospheric C sequestration may increase. For example, a Chinese temperate grassland after 20 years of grazing exclusion had increased its C storage in the top 40 cm of soil by 35.7%.28 Other research performed on a semiarid, 17-year grazer-excluded grassland in northwest China found similar benefits to sequestration of C and nitrogen (N). The researchers state: “Our results showed that the aboveground biomass, root biomass and plant litter were 70–92%, 56–151% and 59–141% higher, respectively, in grazer excluded grass-land than in grazed grassland. Grazing exclusion significantly increased C and N stored in plant biomass and litter and increased the concentrations and stocks of C and N in soils. Grazing exclusion thus significantly increased the C and N stored in grassland ecosystems. The increase in C and N stored in soil contributed to more than 95% and 97% of the increases in ecosystem C and N storage.”29
Microbiotic crusts,30 which were once prevalent across deserts of the American West, “can be dominant sources of productivity and C sequestration in extremely dry environments.”31 But more than a hundred years of trampling by cattle has markedly reduced the presence of these crusts. And even when cattle impacts are removed, crusts may require from 40 to 250 years to fully recover,32 depending on environmental conditions. Consequently, significant C sequestration by the crusts may not be achieved until many years after the removal of cattle.
Quantifying the biological and chemical processes of these and other greenhouse gas sources and sinks following the cessation of cattle grazing would be a daunting task—one made even more difficult by the need to anticipate impacts on vegetation and wildlife from global climate change.




The author thanks T. Shuman for his comments on previous drafts of this essay.