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In the USA, the southeastern states are most vulnerable to the costly impacts from human-caused climate change

Humans are causing Earth’s climate to change. We know that. We’ve known it for decades. Okay so what? The follow-up questions should be directed to what the effects of warming will be. What will the costs be to society, to the natural biosystem, and to human lives? Let’s be honest, if the consequences of warming are not large, then who cares? But, if the consequences are severe, then we should take action now to reduce the warming. This really comes down to costs and benefits. Are the benefits of reducing emissions greater or less than the costs?

But there is a nuance to the answer. The costs are not uniformly distributed. Some regions will suffer more and other regions will suffer less. In fact, some regions will actually benefit in a warming climate. We understand that the world is interconnected and costs will inevitably be shared to some extent. But it is clear we won’t all suffer the same.

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Sandy, Bedfordshire Nectar shoppers flutter out of nowhere, a mass of moths, midges and mosquitoes chopping across the torchlit path

Under a moonless, starless, benighted sky, head torches were switched on and we struck out across the riverside meadow. We had walked for several sure-footed minutes along a closely grazed towpath where white yarrow rosettes glowed like solar garden lights. The only hazards on that firm ground had been the nearly invisible giant plates that I stepped on and found to have hard crusts and soft hearts.

Related: Country diary: Sandy, Bedfordshire: The river is my guiding light

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Yesterday was an historic day for Victoria’s energy future. And there’s more good news on the way. Not that you would know it from listening to federal energy minister.

As industry rejects Standards Australia home battery ban proposal, AEMC calls for new body to govern standards for distributed energy market.

Windlab has become entitled to receive a milestone success payment of just over $10 million in respect of the Coopers Gap Wind Farm.

The Department of Energy’s study on grid reliability and resilience offers an incomplete picture of our grid’s transformation.

The previously-protected area is bigger than Denmark and is thought to be rich in gold.

In the real world, clean coal remains a fantasy, but in Trump world you can mine it, and then the workers "clean" it.

As Australian households flock to solar, interest in battery storage is starting to ramp up, as a way to minimise grid electricity consumption and to provide a reliable source of back-up power.

WA’s biggest piggery operator to add wind and storage to existing solar arrays in push to 100 per cent renewable energy supply.

Campaigners in Poland are worried about the future of one of Europe's last primeval forests, as the Polish government defies an EU order to stop logging there.

The analysis of large amounts of ice from Antarctica's Taylor Valley has helped scientists to tease apart the natural and human-made sources of the potent greenhouse gas methane. Hinrich Schaefer, CC BY-ND

The fossil fuel industry is a larger contributor to atmospheric methane levels than previously thought, according to our research which shows that natural seepage of this potent greenhouse gas from oil and gas reservoirs is more modest than had been assumed.

In our research, published in Nature today, our international team studied Antarctic ice dating back to the last time the planet warmed rapidly, roughly 11,000 years ago.

Katja Riedel and Hinrich Schaefer discuss NIWA’s ice coring work at Taylor Glacier in Antarctica.

We found that natural seepage of methane from oil and gas fields is much lower than anticipated, implying that leakage caused by fossil fuel extraction has a larger role in today’s emissions of this greenhouse gas.

However, we also found that vast stores of methane in permafrost and undersea gas hydrates did not release large amounts of their contents during the rapid warming at the end of the most recent ice age, relieving fears of a catastrophic methane release in response to the current warming.

The ice is processed in a large melter before samples are shipped back to New Zealand. Hinrich Schaefer, CC BY-ND

A greenhouse gas history

Methane levels started to increase with the industrial revolution and are now 2.5 times higher than they ever were naturally. They have caused one-third of the observed increase in global average temperatures relative to pre-industrial times.

If we are to reduce methane emissions, we need to understand where it comes from. Quantifying different sources is notoriously tricky, but it is especially hard when natural and human-driven emissions happen at the same time, through similar processes.

Read more: Detecting methane leaks with infrared cameras: they’re fast, but are they effective

The most important of these cases is natural methane seepage from oil and gas fields, also known as geologic emissions, which often occurs alongside leakage from production wells and pipelines.

The total is reasonably well known, but where is the split between natural and industrial?

To make matters worse, human-caused climate change could destabilise permafrost or ice-like sediments called gas hydrates (or clathrates), both of which have the potential to release more methane than any human activity and reinforce climate change. This scenario has been hypothesised for past warming events (the “clathrate gun”) and for future runaway climate change (the so-called “Arctic methane bomb”). But how likely are these events?

Antarctic ice traps tiny bubbles of air, which represents a sample of ancient atmospheres. Hinrich Schaefer, CC BY-ND The time capsule

To find answers, we needed a time capsule. This is provided by tiny air bubbles enclosed in polar ice, which preserve ancient atmospheres. By using radiocarbon (14C) dating to determine the age of methane from the end of the last ice age, we can work out how much methane comes from contemporary processes, like wetland production, and how much is from previously stored methane. During the time the methane is stored in permafrost, sediments or gas fields, the 14C decays away so that these sources emit methane that is radiocarbon-free.

In the absence of strong environmental change and industrial fossil fuel production, all radiocarbon-free methane in samples from, say, 12,000 years ago will be from geologic emissions. From that baseline, we can then see if additional radiocarbon-free methane is released from permafrost or hydrates during rapid warming, which occurred around 11,500 years ago while methane levels shot up.

Tracking methane in ice

The problem is that there is not much air in an ice sample, very little methane in that air, and a tiny fraction of that methane contains a radiocarbon (14C) atom. There is no hope of doing the measurements on traditional ice cores.

Our team therefore went to Taylor Glacier, in the Dry Valleys of Antarctica. Here, topography, glacier flow and wind force ancient ice layers to the surface. This provides virtually unlimited sample material that spans the end of the last ice age.

A tonne of ice yielded only a drop of methane. Hinrich Schaefer, CC BY-ND

For a single measurement, we drilled a tonne of ice (equivalent to a cube with one-metre sides) and melted it in the field to liberate the enclosed air. From the gas-tight melter, the air was transferred to vacuum flasks and shipped to New Zealand. In the laboratory, we extracted the pure methane out of these 100-litre air samples, to obtain a volume the size of a water drop.

Only every trillionth of the methane molecules contains a 14C atom. Our collaborators in Australia were able to measure exactly how big that minute fraction is in each sample and if it changed during the studied period.

Low seepage, no gun, no bomb

Because radiocarbon decays at a known rate, the amount of 14C gives a radiocarbon age. In all our samples the radiocarbon date was consistent with the sample age.

Radiocarbon-free methane emissions did not increase the radiocarbon age. They must have been very low in pre-industrial times, even during a rapid warming event. The latter indicates that there was no clathrate gun or Arctic methane bomb going off.

So, while today’s conditions differ from the ice-covered world 12,000 years ago, our findings implicate that permafrost and gas hydrates are not too likely to release large amounts of methane in future warming. That is good news.

Wetlands must have been responsible for the increase in methane at the end of the ice age. They have a lesser capacity for emissions than the immense permafrost and clathrate stores.

Geologic emissions are likely to be lower today than in the ice age, partly because we have since drained shallow gas fields that are most prone to natural seepage. Yet, our highest estimates are only about half of the lower margin estimated for today. The total assessment (natural plus industrial) for fossil-fuel methane emissions has recently been increased.

In addition, we now find that a larger part of that must come from industrial activities, raising the latter to one third of all methane sources globally. For comparison, the last IPCC report put them at 17%.

Measurements in modern air suggest that the rise in methane levels over the last years is dominated by agricultural emissions, which must therefore be mitigated. Our new research shows that the impact of fossil fuel use on the historic methane rise is larger than assumed. In order to mitigate climate change, methane emissions from oil, gas and coal production must be cut sharply.

Hinrich Schaefer works for the National Institute of Water and Atmospheric Research. He has received funding from the New Zealand Government through Strategic Science Investment Funds and a Marsden Grant. In previous positions, his work has received government funding from Germany, the European Union, Canada and the USA, as well as a grant from the American Chemical Society.