Antartica is a “natural reserve, devoted to peace and science”, according to the Antarctic Treaty System. This complex set of agreements collectively takes a firm stance on conservation, exemplified by the Convention on the Conservation of Marine Living Resources. Adopted in 1980, this convention was negotiated rapidly in response to expanding trawling of Antarctic krill (Euphausia superba). Krill are at the base of the region’s marine food web, so there were worries that a dearth of the small crustaceans would threaten the whole ecosystem, especially whales.

Of the common adjectives used to describe Earth’s southern polar region, ‘pristine’ is among the most inappropriate. The ocean around Antarctica bobs with pieces of microplastic pollution, and for decades, whales and other marine life have been stripped from the sea. The ozone hole gapes above. To find any of the advertised unspoiled wilderness, a visitor has to trek inshore and away from the direct influence of the rest of the world. Because there is another misapplied label: remote.

A growing network of ice cores reveals the past 800,000 years of Antarctic climate and atmospheric composition. The data show tight links among greenhouse gases, aerosols and global climate on many timescales, demonstrate connections between Antarctica and distant locations, and reveal the extraordinary differences between the composition of our present atmosphere and its natural range of variability as revealed in the ice core record.

As the Earth’s atmosphere warms, the atmospheric circulation changes. These changes vary by region and time of year, but there is evidence that anthropogenic warming causes a general weakening of summertime tropical circulation. Because tropical cyclones are carried along within their ambient environmental wind, there is a plausible a priori expectation that the translation speed of tropical cyclones has slowed with warming.

Freshwater availability is changing worldwide. Here we quantify 34 trends in terrestrial water storage observed by the Gravity Recovery and Climate Experiment (GRACE) satellites during 2002–2016 and categorize their drivers as natural interannual variability, unsustainable groundwater consumption, climate change or combinations thereof. Several of these trends had been lacking thorough investigation and attribution, including massive changes in northwestern China and the Okavango Delta. Others are consistent with climate model predictions.

The Montreal Protocol was designed to protect the stratospheric ozone layer by enabling reductions in the abundance of ozone-depleting substances such as chlorofluorocarbons (CFCs) in the atmosphere. The reduction in the atmospheric concentration of trichlorofluoromethane (CFC-11) has made the second-largest contribution to the decline in the total atmospheric concentration of ozone-depleting chlorine since the 1990s.

Making sense of recent energy trends can seem like a high-stakes Rorschach test. Some experts see the boom in renewable energy and the shift away from coal in many countries as evidence that the world is beginning to turn a corner on global warming. Others see simply a continuing reliance on low-cost fossil fuels, slow governmental action and a rising risk of planetary meltdown.

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Global warming is rapidly emerging as a universal threat to ecological integrity and function, highlighting the urgent need for a better understanding of the impact of heat exposure on the resilience of ecosystems and the people who depend on them. Here we show that in the aftermath of the record-breaking marine heatwave on the Great Barrier Reef in 2016, corals began to die immediately on reefs where the accumulated heat exposure exceeded a critical threshold of degree heating weeks, which was 3–4 °C-weeks.

The Atlantic meridional overturning circulation (AMOC)—a system of ocean currents in the North Atlantic—has a major impact on climate, yet its evolution during the industrial era is poorly known owing to a lack of direct current measurements. Here we provide evidence for a weakening of the AMOC by about 3 ± 1 sverdrups (around 15 per cent) since the mid-twentieth century.

Drug regulators and trial designs should assess benefits that actually matter to people with cancer, says Ajay Aggarwal.

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