419.14 ppm: tracking weekly climate news

Welcome to the first in our new regular segment on new climate science stories you might have missed. The title refers to the average global concentration of carbon dioxide within the Earth’s atmosphere in parts per million (ppm). Meaning that for every million air particles, currently 419.14 of them are CO₂.

UK plants flower a month earlier due to climate change

Climate change is causing plants in the UK to flower a month earlier on average, which could have dire consequences for wildlife, agriculture and everyday gardeners.

In a new study published in Proceedings of the Royal Society B, this analysis was based on over 400,000 observations of 406 plant species by citizen scientists – with records going back to the mid-18^th century.

The research team found that the average first flowering date from 1987 to 2019 – the period coinciding with accelerated global warming caused by human activities – is a full month earlier than from 1753 to 1986.

“The results are truly alarming, because of the ecological risks associated with earlier flowering times,” says lead author Professor Ulf Büntgen from the University of Cambridge, UK.

“When plants flower too early, a late frost can kill them – a phenomenon that most gardeners will have experienced at some point. But the even bigger risk is ecological mismatch,” he says.

“Plants, insects, birds and other wildlife have co-evolved to a point that they’re synchronised in their development stages. When a certain plant flowers, it attracts a particular type of insect, which attracts a particular type of bird, and so on. But if one component responds faster than the others, there’s a risk that they’ll be out of synch, which can lead species to collapse if they can’t adapt quickly enough.”

The data was collated through Nature’s Calendar, where anyone in the UK can log their observations of plants and wildlife, which is important because the long-term effects of climate change on ecosystems are subtle and not always easy to recognise (why not get involved with an ecological citizen science project and contribute to research like this where you live?)

Drought-tolerant crops provide better nutrition and more sustainable agriculture

Researchers have found that shifting people’s diets to include more drought-tolerant grains (like maize, sorghum and millet) and to whole grains would lead to significant increases in dietary nutrients, while also helping to lower the environmental footprint of crop production.

Researchers have shown in a new paper, published in Environmental Research Letters, that country-specific shifts in cereal supply – which account for more than 40% of dietary calories, protein, iron, and zinc worldwide – could contribute to more environmentally sustainable diets.

By looking at historical data from the Global Expanded Nutrient Supply database, including 152 countries (accounting for 96% of the world population) from 1961 to 2011, and taking into account the dietary scenarios at the country level, they were able to understand which dietary shifts would be locally acceptable and feasible.

“We wanted to take the local preferences and the cultural acceptance into consideration because that will increase the chances that sustainable diets will actually be accepted,” says lead author and PhD candidate Dongyang Wei, of the University of Delaware in the US.

Unlike thirsty cereals like rice and wheat, these drought-tolerant crops use water more efficiently, release less greenhouse gases during their production, and can maintain their nutrient content despite elevated CO₂ in the atmosphere.

By looking at only crops that have been and are still cultivated and consumed within each country, it might be possible to identify locally acceptable dietary shifts which could lead to both environmental and human health benefits.

Replacing animals in the global food system could put the brakes on climate change

A global switch from animal-based to plant-based diet would have a substantial impact on stabilising greenhouse gas emissions – halting their increase for 30 years, according to a new study published in PLoS Climate.

The study looked at the impact of both eliminating the emissions linked to animal agriculture and restoring native vegetation on 30% of the Earth’s land surface currently used to house and feed livestock.

Using publicly available data – livestock production, emissions, and the recovery potential for biomass on land which is currently used for livestock – they found that phasing out animal agriculture over the next 15 years would provide 52% of the net emissions reductions necessary to limit global warming to 2°C above pre-industrial levels (the minimum threshold to avert disastrous climate change).

Although this complete phase-out was projected to have the largest impact, even 90% of the emissions reductions could be achieved by only replacing ruminants like cattle and sheep.

While this sounds great in theory, the paper does not explore the particulars of what a global phase-out of animal agriculture would entail practically. It should also be noted that both authors stand to benefit financially from the reduction of animal agriculture, as they are both involved in Impossible Foods – a company developing alternatives to animals in food production.

Cooking with gas is not so great

Natural gas appliances generate CO₂ by burning gas as fuel and leaking unburnt methane into the air. A new study has revealed that this methane leakage inside US homes has a climate impact comparable to the CO₂ emissions from about 500,000 petrol-powered cars.

Crucially, more than three-quarters of the emissions happened while the stoves were turned off, due to leakages from gas fittings, connections and in-home gas lines.

These findings, published in Environmental Science & Technology, warn that natural gas is not only an overlooked contributor to global warming, but also a source of indoor air pollutants.

“I don’t want to breathe any extra nitrogen oxides, carbon monoxide or formaldehyde,” says senior author  Rob Jackson, professor of Earth system science at Stanford University, in the US.

“Why not reduce the risk entirely? Switching to electric stoves will cut greenhouse gas emissions and indoor air pollution.”

If that’s not possible, using your stove hood for kitchen ventilation can help reduce these concentrations and improve air quality in your home.

Antarctica’s sea-ice paradox finally explained

Despite global warming and the loss of sea-ice in the Arctic, Antarctic sea-ice has remained largely unchanged since 1979 – challenging existing climate model-based simulations which indicate significant loss.

But scientists have now shown that the warming of the ocean around Antarctica has been dampened by the transport of additional heat northwards toward the equator – more so than what has been previously estimated by lower-resolution simulations that only included simplified versions of the ocean eddies which influence this phenomenon.

In a study published in Nature Communications, they applied the AWI Climate Model (AWI-CM), which unlike other climate models allows certain key regions like the Southern Ocean to be simulated in high resolution.

“We used a broad range of configurations for our simulations. In the process, it became clear that only those simulations with a high-resolution description of the Southern Ocean encircling the Antarctic produced delayed sea-ice loss similar to what we are seeing in reality,” says first author Thomas Rackow from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), Germany.

“When we then extended the model into the future, even under a highly unfavourable greenhouse-gas scenario, the Antarctic sea-ice cover remains largely stable until mid-century. After that point the sea ice retreats rather rapidly, just as the Arctic sea ice has been doing for decades.”

This research provides the basis for improved simulations and forecasts for the future of the Antarctic.