To save the planet, we need to cut methane emissions from agriculture, too

Mmm, farmy. Image: Getty.

Methane concentrations in the atmosphere are growing faster than any time in the past 20 years. The increase is largely driven by the growth in food production, according to the Global Methane Budget released in December. Methane is contributing less to global warming than carbon dioxide (CO₂), but it is a very powerful greenhouse gas.

Since 2014, methane concentrations in the atmosphere have begun to track the most carbon-intensive pathways developed for the 21st century by the Intergovernmental Panel on Climate Change (IPCC). The growth of methane emissions from human activities comes at a time when CO₂ emissions from burning fossil fuels have stalled over the past three years.

If these trends continue, methane growth could become a dangerous climate wildcard, overwhelming efforts to reduce CO₂ in the short term.

Methane concentration pathways from IPCC and observations from the NOAA measuring network (Saunois et al 2016, Environmental Research Letters). The projected global warming range by the year 2100, relative to 1850-1900, is shown for each pathway.

In two papers published on 12 December (see here and here), we bring together the most comprehensive ensemble of data and models to build a complete picture of methane and where it is going – the global methane budget. This includes all major natural and human sources of methane, and the places where it ends up in methane “sinks” such as the atmosphere and the land.

This work is a companion effort to the global CO₂ budget published annually, both by international scientists under the Global Carbon Project.

Where does all the methane go?

Methane is emitted from multiple sources, mostly from land, and accumulates in the atmosphere. In our greenhouse gas budgets, we look at two important numbers.

First, we look at emissions (which activities are producing greenhouse gases).

Second, we look at where this gas ends up. The important quantity here is the accumulation (concentration) of methane in the atmosphere, which leads to global warming. The accumulation results from the difference between total emissions and the destruction of methane in the atmosphere and uptake by soil bacteria.

CO₂ emissions take centre stage in most discussions to limit climate change. The focus is well justified, given that CO₂ is responsible for more than 80 per cent of global warming due to greenhouse gases. The concentration of CO₂ in the atmosphere (now around 400 parts per million) has risen by 44 per cent since the Industrial Revolution (around the year 1750).

While CO₂ in the atmosphere has increased steadily, methane concentrations grew relatively slowly throughout the 2000s, but since 2007 have grown ten times faster. Methane increased faster still in 2014 and 2015.

Remarkably, this growth is occurring on top of methane concentrations that are already 150 per cent higher than at the start of the Industrial Revolution (now around 1,834 parts per billion).

The global methane budget is important for other reasons too: it is less well understood than the CO₂ budget and is influenced to a much greater extent by a wide variety of human activities. About 60 per cent of all methane emissions come from human actions.

These include living sources – such as livestock, rice paddies and landfills – and fossil fuel sources, such as emissions during the extraction and use of coal, oil and natural gas.

We know less about natural sources of methane, such as those from wetlands, permafrost, termites and geological seeps. Biomass and biofuel burning originates from both human and natural fires.

Global methane budget 2003-2012 based on Saunois et al. 2016, Earth System Science Data. See the Global Carbon Atlas.

Given the rapid increase in methane concentrations in the atmosphere, what factors are responsible for its increase?

Uncovering the causes

Scientists are still uncovering the reasons for the rise. Possibilities include: increased emissions from agriculture, particularly from rice and cattle production; emissions from tropical and northern wetlands; and greater losses during the extraction and use of fossil fuels, such as from fracking in the United States. Changes in how much methane is destroyed in the atmosphere might also be a contributor.

Our approach shows an emerging and consistent picture, with a suggested dominant source along with other contributing secondary sources.

First, carbon isotopes suggest a stronger contribution from living sources than from fossil fuels. These isotopes reflect the weights of carbon atoms in methane from different sources. Methane from fossil fuel use also increased, but evidently not by as much as from living sources.

Second, our analysis suggests that the tropics were a dominant contributor to the atmospheric growth. This is consistent with the vast agricultural development and wetland areas found there (and consistent with increased emissions from living sources).

This also excludes a dominant role for fossil fuels, which we would expect to be concentrated in temperate regions such as the US and China. Those emissions have increased, but not by as much as from tropical and living sources.

Third, state-of-the-art global wetland models show little evidence for any significant increase in wetland emissions over the study period.

The overall chain of evidence suggests that agriculture, including livestock, is likely to be a dominant cause of the rapid increase in methane concentrations. This is consistent with increased emissions reported by the Food and Agriculture Organisation and does not exclude the role of other sources.

Remarkably, there is still a gap between what we know about methane emissions and methane concentrations in the atmosphere. If we add all the methane emissions estimated with data inventories and models, we get a number bigger than the one consistent with the growth in methane concentrations. This highlights the need for better accounting and reporting of methane emissions.

We also don’t know enough about emissions from wetlands, thawing permafrost and the destruction of methane in the atmosphere.


The way forward

At a time when global CO₂ emissions from fossil fuels and industry have stalled for three consecutive years, the upward methane trend we highlight in our new papers is unwelcome news. Food production will continue to grow strongly to meet the demands of a growing global population and to feed a growing global middle class keen on diets richer in meat.

However, unlike CO₂, which remains in the atmosphere for centuries, a molecule of methane lasts only about 10 years.

This, combined with methane’s super global warming potency, means we have a massive opportunity. If we cut methane emissions now, this will have a rapid impact on methane concentrations in the atmosphere, and therefore on global warming.

There are large global and domestic efforts to support more climate-friendly food production with many successes, ample opportunities for improvement, and potential game-changers.

However, current efforts are insufficient if we are to follow pathways consistent with keeping global warming to below 2℃. Reducing methane emissions needs to become a prevalent feature in the global pursuit of the sustainable future outlined in the Paris Agreement.The Conversation

Pep Canadell is executive director of the Global Carbon Project, CSIRO. Ben Poulter is a research scientist at NASA. Marielle Saunois is a researcher in environmental science at the University of Versailles Saint Quentin. Paul Krummel is research group leader at CSIRO. Philippe Bousquet is a professor of environment scinece at the University of Versailles Saint-Quentin en Yvelines. Rob Jackson is chair of the Global Carbon Project at Stanford University.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

How can we stop city breaks killing our cities?

This couple may look happy, but they’re destroying Barcelona. Image: Getty.

Can’t wait to pack your bags and head off on holiday again? It used to be that people would look forward to a long break in summer – but now tourists have got used to regular short breaks through the year. We love to jet off to the world’s glittering cities, even if only for a day or two. The trouble is, binge travelling may be killing the places we visit.

You may even have seen some “tourists go home” graffiti on your last trip, and it’s not hard to see why. Barcelona is a good example of how a city can groan under the weight of its popularity. It now has the busiest cruise port, and the second fastest growing airport in Europe. Walking through the Barcelona streets at peak season (which now never seems to end) flings you into a relentless stream of tourists. They fill the city’s hot spots in search of “authentic” tapas and sangria, and a bit of culture under the sun. The mayor has echoed residents’ concerns over the impact of tourism; a strategic plan has been put in place.

It is true though, that cities tend to start managing the impact of tourism only when it is already too late. It creeps up on them. Unlike visitors to purpose-built beach destinations and national parks, city-break tourists use the same infrastructure as the locals: existing systems start slowly to stretch at the seams. Business travellers, stag parties and museum visitors will all use existing leisure facilities.

‘Meet the friendly locals’, they said. Image: Sterling Ely/Flickrcreative commons.

Barcelona may only be the 59th largest city in the world, but it is the 12th most popular with international visitors. Compared to London or Paris, it is small, and tourism has spiked sharply since the 1992 Olympics rather than grown steadily as in other European favourites like Rome.

Growth is relentless. The UN World Tourism Organisation (UNWTO) even speaks about tourism as a right for all citizens, and citizens are increasingly exercising that right: from 1bn international travellers today, we will grow to 1.8bn by 2030, according to UNWTO forecasts.

Faced with this gathering storm, just who is tourism supposed to benefit? Travellers, cities, residents or the tourism industry?

Market forces

Managing the impact of tourism starts by changing the way destinations market themselves: once the tourists arrive, it’s too late. Tourism authorities need to understand that they are accountable to the city, not to the tourism industry. When the city of Barcelona commissioned the University of Surrey to look into how it might best promote sustainable development, we found a series of techniques which have been incorporated, at least in part, into the city’s 2020 Tourism Strategy.

In the simplest terms, the trick is to cajole tourists into city breaks which are far less of a burden on the urban infrastructure. In other words, normalising the consumption of sustainable tourism products and services. In Copenhagen, 70 per cent of the hotels are certified as sustainable and the municipal authority demands sustainability from its suppliers.

Higher than the sun. A primal scream from the world’s cities? Image: Josep Tomàs/Flickr/creative commons.

Destinations must also be accountable for the transport impact of their visitors. The marketing department might prefer a Japanese tourist to Barcelona because on average they will spend €40 more than a French tourist – according to unpublished data from the Barcelona Tourist Board – but the carbon footprint we collectively pay for is not taken into account.

Crucially, for the kind of city breaks we might enjoy in Barcelona, most of the carbon footprint from your holiday is from your transport. Short breaks therefore pollute more per night, and so destinations ought to be fighting tooth and nail to get you to stay longer. It seems like a win for tourists too: a few extra days in the Spanish sun, a more relaxing break, and all accompanied by the warm glow of self-satisfaction and a gold star for sustainability.


Destinations can also target customers that behave the most like locals. Japanese first-time visitors to Barcelona will crowd the Sagrada Familia cathedral, while most French tourists are repeat visitors that will spread out to lesser-known parts of the city. Reducing seasonality by emphasising activities that can be done in winter or at less crowded times, and geographically spreading tourism by improving less popular areas and communicating their particular charms can also help reduce pressure on hot spots, much like Amsterdam is doing.

Turnover is vanity, and profit margins are sanity. No city should smugly crow about the sheer volume of visitors through its gates. If tourism is here to stay, then the least cities can do is to sell products that will have the greatest benefit for society. Whether it’s Barcelona, Berlin, Bologna or Bognor, there should be a focus on locally and ethically produced products and services which residents are proud to sell. Tourist boards should work with small businesses that offer creative and original things to do and places to stay, adding breadth to the city’s offering.

The ConversationWhether Barcelona will introduce these ideas will depend on the bravery of politicians and buy-in from the powerful businesses which are happily making short-term profits at the expense of residents and the planet. It is possible to do things differently, and for everyone to benefit more. It may be that the tipping point lies in the age-old mechanics of supply and demand: bear that in mind next time you’re booking a quick city break that looks like it’s only adding to the problem.

Xavier Font is professor of marketing at the University of Surrey.

This article was originally published on The Conversation. Read the original article.