Jules Verne sent his fictional submarine, the Nautilus, to the South Pole through a hidden ocean beneath a thick ice cap.

The Arctic heat wave that sent Siberian temperatures soaring to around 100 degrees Fahrenheit on the first day of summer put an exclamation point on an astonishing transformation of the Arctic environment that’s been underway for about 30 years.

Heat may kill more people in the US than previously reported, according to a new study.

There is a lot of discussion on the benefits of electric cars versus fossil fuel cars in the context of lithium mining. Please can you tell me which one weighs in better on the environmental impact in terms of global warming and why?

Every car has an optimal speed range that results in minimum fuel consumption, but this range differs between vehicle types, design and age.

For airlines, the reckoning is no longer far away on the horizon. It’s now a jumbo jet meters from the runway, landing gear down.

The Australian government’s investment roadmap for low-emissions technologies promises more taxpayers’ money to the gas industry but fails to deliver the policy needed for people to support a transition to renewable energy.

If I were to buy an electric vehicle it would add to the load on the national grid. Is the only way we are currently able to add the extra power to burn more coal?

Ice shelves, massive floating bodies of ice, are well-known for their buffering effect on land-based ice sheets as they slow their flow towards the sea.

Green growth has emerged as the dominant narrative for tackling contemporary environmental problems.

The tornadoes that swept across the Southeast this spring were a warning to communities nationwide:

Summer temperatures in Chicago normally peak in the low 80s, but in mid-July 1995 they topped 100 F with excessive humidity for three days straight.

COVID-19 has radically changed our travel habits in just a matter of weeks. Walking and cycling are up, as people enjoy their daily exercise or take essential journeys they might otherwise have made by public transport.

When the southern Great Plains of the US were blighted with a series of droughts in the 1930s, it had an unparalled impact on the whole country.

The numbers of people cycling and walking in public spaces during COVID-19 has skyrocketed.

The explosive growth and success of human society over the past 10,000 years has been underpinned by a distinct range of climate conditions.

Climate scientists use mathematical models to project the Earth’s future under a warming world, but a group of the latest models have included unexpectedly high values for a measure called “climate sensitivity”.

Earth had several periods of high carbon dioxide levels in the atmosphere and high temperatures over the last several million years.

Humans are amazing creatures, in that they have show they can live in almost any climate.

Changes in ocean circulation may have caused a shift in Atlantic Ocean ecosystems not seen for the past 10,000 years, new analysis of deep-sea fossils has revealed.

Agriculture has long been framed in the global climate action discussion as a sector whose activities conflict with meeting greenhouse gas (GHG) reduction targets.

Politicians and business people are fond of making promises to plant thousands of trees to slow climate change. But who actually plants those trees, and who tends them as they grow?

Author supplied

The Australian summer just gone will be remembered as the moment when human-caused climate change struck hard. First came drought, then deadly bushfires, and now a bout of coral bleaching on the Great Barrier Reef – the third in just five years. Tragically, the 2020 bleaching is severe and the most widespread we have ever recorded.

Coral bleaching at regional scales is caused by spikes in sea temperatures during unusually hot summers. The first recorded mass bleaching event along Great Barrier Reef occurred in 1998, then the hottest year on record.

Since then we’ve seen four more mass bleaching events – and more temperature records broken – in 2002, 2016, 2017, and again in 2020.

This year, February had the highest monthly sea surface temperatures ever recorded on the Great Barrier Reef since the Bureau of Meteorology’s records began in 1900.

Coral bleaching at Magnetic Island, March 2020. (Video by Victor Huertas)

Not a pretty picture

We surveyed 1,036 reefs from the air during the last two weeks in March, to measure the extent and severity of coral bleaching throughout the Great Barrier Reef region. Two observers, from the ARC Centre of Excellence for Coral Reef Studies and the Great Barrier Reef Marine Park Authority, scored each reef visually, repeating the same procedures developed during early bleaching events.

The accuracy of the aerial scores is verified by underwater surveys on reefs that are lightly and heavily bleached. While underwater, we also measure how bleaching changes between shallow and deeper reefs.

Of the reefs we surveyed from the air, 39.8% had little or no bleaching (the green reefs in the map). However, 25.1% of reefs were severely affected (red reefs) – that is, on each reef more than 60% of corals were bleached. A further 35% had more modest levels of bleaching.

Bleaching isn’t necessarily fatal for coral, and it affects some species more than others. A pale or lightly bleached coral typically regains its colour within a few weeks or months and survives.

The 2020 coral bleaching event was the second-worst in more than two decades. ARC Centre of Excellence for Coral Reef Studies

But when bleaching is severe, many corals die. In 2016, half of the shallow water corals died on the northern region of the Great Barrier Reef between March and November. Later this year, we’ll go underwater to assess the losses of corals during this most recent event.

Compared to the four previous bleaching events, there are fewer unbleached or lightly bleached reefs in 2020 than in 1998, 2002 and 2017, but more than in 2016. Similarly, the proportion of severely bleached reefs in 2020 is exceeded only by 2016. By both of these metrics, 2020 is the second-worst mass bleaching event of the five experienced by the Great Barrier Reef since 1998.

The unbleached and lightly bleached (green) reefs in 2020 are predominantly offshore, mostly close to the edge of the continental shelf in the northern and southern Great Barrier Reef. However, offshore reefs in the central region were severely bleached again. Coastal reefs are also badly bleached at almost all locations, stretching from the Torres Strait in the north to the southern boundary of the Great Barrier Reef Marine Park.

CC BY-ND

For the first time, severe bleaching has struck all three regions of the Great Barrier Reef – the northern, central and now large parts of the southern sectors. The north was the worst affected region in 2016, followed by the centre in 2017.

In 2020, the cumulative footprint of bleaching has expanded further, to include the south. The distinctive footprint of each bleaching event closely matches the location of hotter and cooler conditions in different years.

Poor prognosis

Of the five mass bleaching events we’ve seen so far, only 1998 and 2016 occurred during an El Niño – a weather pattern that spurs warmer air temperatures in Australia.

But as summers grow hotter under climate change, we no longer need an El Niño to trigger mass bleaching at the scale of the Great Barrier Reef. We’ve already seen the first example of back-to-back bleaching, in the consecutive summers of 2016 and 2017. The gap between recurrent bleaching events is shrinking, hindering a full recovery.

For the first time, severe bleaching has struck all three regions of the Great Barrier Reef. ARC Centre of Excellence for Coral Reef Studies

After five bleaching events, the number of reefs that have escaped severe bleaching continues to dwindle. Those reefs are located offshore, in the far north and in remote parts of the south.

The Great Barrier Reef will continue to lose corals from heat stress, until global emissions of greenhouse gasses are reduced to net zero, and sea temperatures stabilise. Without urgent action to achieve this outcome, it’s clear our coral reefs will not survive business-as-usual emissions.

About The Author

Terry Hughes, Distinguished Professor, James Cook University and Morgan Pratchett, Professor, ARC Centre of Excellence for Coral Reef Studies, James Cook University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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