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New research suggests that limiting global warming to 1.5℃ rather than letting it reach 2℃ could make a significant difference to the severity of extreme weather events in Australia, and could make all the difference for the Great Barrier Reef.

The solar PV cost reduction spiral reached its lowest point yet at an auction in Chile last week, where a Spanish developer won contracts to sell power from a solar plant high in the Andes for $29.10/MWh.

Can treating the immune system lead to a revolution in treating depression?

SEAL SCIENCE: A group of elephant seals in Antarctica has helped show how freshwater from melting ice shelves affects a key part of the engine that drives the circulation of the world's oceans.

Detecting traces of perfume could help in the fight against crime, a study suggests

A worldwide ban on plastic microbeads in cosmetics should be imposed as soon as possible, MPs demand.

Environmental audit committee calls for ban after hearing that microbeads harm marine life and enter the food chain

Cosmetics companies must be banned from using plastic microbeads in scrubs, toothpaste and beauty products because of the marine pollution they are causing, say a group of MPs.

Members of the environmental audit committee have called for a ban within 18 months after hearing that trillions of tiny pieces of plastic are accumulating in the world’s oceans, lakes and estuaries, harming marine life and entering the food chain. About 86 tonnes of microplastics are released into the environment every year in the UK from facial exfoliants alone, they were told.

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Hundreds of thousands of fish, commonly known as peanut bunker fish, have washed up dead in a New Jersey creek.

In Hawaii, large numbers of tourists disturb nocturnal spinner dolphins, which continue moving while they snooze

The federal government is proposing a ban on swimming with dolphins in Hawaii – a move that may crush the dreams of many tourists, but will allow the marine mammals to finally get a good day’s sleep.

The proposed rule would bar people from swimming or approaching within 50 yards of the Hawaiian spinner dolphin. The dolphins are an increasingly popular attraction for tourists, who pay for chartered tours of the bays the dolphins frequent.

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• Rain cold and high winds destroy 133 acres of trees west of Mexico City
• March storms killed 7% of monarchs and added to habit loss by tree-felling

Storms earlier this year blew down more than a hundred acres of forests where migrating monarch butterflies spend the winter in central Mexico, killing more than 7% of the monarchs, according to conservationists.

Rain, cold and high winds from the storms caused the loss of 133 acres (54 hectares) of pine and fir trees in the forests west of Mexico City, more than four times the amount lost to illegal logging this year. It was the biggest storm-related loss since the winter of 2009-10, when unusually heavy rainstorms and mudslides caused the destruction of 262 acres (106 hectares) of trees.

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Antarctica's ice sheets will continue to melt long after this century. Antarctica image from www.shutterstock.com

The Paris climate agreement set a “safe” global warming limit of below 2℃, aiming below 1.5℃ by 2100. The world has already warmed about a degree since the Industrial Revolution, and on our current emissions trajectory we will likely breach these limits within decades.

However, we could still come back from the brink with a massive effort.

But let’s take a closer look at that warming limit. If we accept that 1.5-2℃ of warming marks the danger threshold, then this is true whether it applies tomorrow, in 2100, or some time thereafter. What we need is to stay below these limits for all time.

Put it this way: we wouldn’t be satisfied if the brakes on a new car only worked on the day of purchase, or for two weeks after that – we expect them to keep us safe throughout the car’s lifetime.

The trouble is, limiting warming to well below 2℃ forever is a much harder job.

Millennia matter

Whatever warming we manage to prevent this century, the world will continue to respond to climate change after 2100.

Looking beyond 2100 is often considered irrelevant, given that electoral timescales only operate over several years, and individual development projects over several decades.

However, it is highly relevant to major infrastructure developments, such as overall city planning. Throughout Europe and Asia, the foundations of most city infrastructure date back centuries, or even millennia. Not incidentally, so do most of the supporting agricultural and fisheries traditions and transport routes.

Even the more recent developments in the Americas, Africa and Australia have fundamental roots that date back hundreds of years. Clearly, we need to think beyond the current century when we think about climate change and its impact on civilisation.

The short and the long of it

The climate system is made up of many different components. Some of these respond rapidly to changes, others over much longer timescales.

The components that respond rapidly to the impacts of greenhouse gas emissions include changes in cloud, snow and sea-ice cover, in dust content of the atmosphere, land-surface changes, and so on. Some work almost instantaneously, others over decades. Together these are known as the “transient” response.

Slow-responding components in the climate system include ocean warming, continental ice-sheets and exchanges of carbon between lifeforms, oceans, the sea floor, soils and the atmosphere. These work over many centuries and are known as the “equilibrium” response.

Large amounts of energy are needed to warm up such a large volume of water as the global ocean. The ocean has taken up more than 90% of all the extra heat caused by greenhouse gases emitted since the Industrial Revolution, especially into the upper few hundred metres.

However, the ocean is so vast that it will continue to warm from the top down over many centuries to millennia, until its energy uptake has adjusted to Earth’s new energy balance. This will continue even if no further emissions are made.

Ice sheets on Antarctica and Greenland respond to climate change like an accelerating heavy freight train: slow to start, and virtually unstoppable once they get going. Climate change has been building up since the onset of the Industrial Revolution, but only in recent decades have we started to see marked mass-loss increases from the ice sheets.

The ice-sheet freight train has at last come up to speed and now it will keep on rolling and rolling, regardless of what immediate actions we take regarding our emissions.

Looking to the past

Carbon dioxide levels have reached 400 parts per million (ppm). To find out what this means for the coming centuries, we have to look between 3 million and 3.5 million years into the past.

Temperature reconstructions suggest the world was 2-3℃ warmer than before the Industrial Revolution, which is similar to the expected equilibrium response for the future.

Geological data from the last 65 million years indicate that the climate warms 3-5℃ for every doubling of CO₂ levels.

Before the Industrial Revolution, CO₂ levels were around 280 ppm. Under all but the most optimistic emission scenarios of the Intergovernmental Panel on Climate Change (IPCC), the first doubling (to 560 ppm) is approached or crossed between the years 2040 and 2070.

While we don’t know exactly how high sea level was 3.5 million years ago, we are confident that it stood at least 10 metres higher than today. Most studies suggest sea-level rise around 1m higher than today by 2100, followed by a relentlessly continued rise by some 2m per century. Even a rise of a metre or more by 2100 is murderously high for global infrastructure, especially in developing countries.

Today, some 600 million people live at elevations within 10m of sea level. The same area generates 10% of the world’s total GDP. It is estimated that a sea-level rise of 2m will displace almost 2.5% of the global population.

Even the more immediate impacts of sea-level rise are enormous. In 136 of the world’s largest port cities, the population exposed to flooding is estimated to increase by more than three times by 2070, due to combined actions of sea-level rise, land subsidence, population growth and urbanisation. The same study estimates a tenfold increase in asset exposure.

Back to the future

The eventual equilibrium (long-term) level of warming is up to twice the transient (short-term) level of warming. In other words, the Paris Agreement’s response of 1.5-2℃ by 2100 will grow over subsequent centuries toward an equilibrium warming of 2.3-4℃, even without any further emissions.

Given that we have already reached 1℃ of warming, if the aim is to avoid dangerous warming beyond 2℃ over the long term, we have to avoid any further warming from now on.

We can’t do this by simply stopping all emissions. This is because there is still some warming to catch up from the slower transient processes. To stop any further warming, we will have to reduce atmospheric CO₂ levels to about 350 ppm. Doing so requires both stopping the almost 3ppm rise per year from new emissions, and implementing carbon capture to pull CO₂ out of the atmosphere.

Global warming would be limited to 1-1.5℃ by 2100, and 2℃ over the long term, and in addition ocean acidification would be kept under control. These are essential for containing the impacts of climate change on global ecosystems.

This is the real urgency of climate change. Fully understanding the challenge can help us get to work.

Eelco Rohling receives funding from the Australian Research Council (ARC) and the UK Natural Environment Research Council (NERC). He is Professor of Ocean and Climate Change at The Australian National University (ANU) and the University of Southampton (UK), and a member of ANU's Climate Change Institute (CCI).

Barack Obama visits Baton Rouge on Tuesday, telling residents affected by historic flooding that the country will continue to support them and help them rebuild their lives. Obama also takes a dig at Donald Trump, saying ‘this is not a photo op issue’ . The floods have killed at least 13 people and damaged tens of thousands of homes

• Obama digs Trump in flood-damaged Louisiana: ‘not a photo-op’ – politics live

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Tourists gather in Transylvania to help with the traditional mountain hay harvest. BBC Gaelic Journalist Teàrlach Quinnell went with them.

In honor of the National Park Service’s centennial this week, the Guardian has compiled scenes from around the country. President Woodrow Wilson signed the act creating the National Park Service 100 years ago. From coast to coast, Hawaii to Maine, the beauty, nature and scope of US national parks are breathtaking

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Most countries in the world have little capacity to deal effectively with invasive species, a study suggests.

Hailed as ‘America’s best idea’, the parks are hugely popular with the public but face political efforts to lift federal protection and allow private development

“It’s easy to feel besieged here,” said Wendy Ross, superintendent of the Theodore Roosevelt national park. Ross’s park, named after the “conservationist president” who helped to keep America’s natural treasures unspoiled, is surrounded by oil and gas drilling that has transformed the landscape.

Related: 100 years of America’s national parks – in pictures

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Corruption in many Pacific countries appears endemic, the Pacific has the world’s fastest growth rate of HIV infection and the Pacific is predicted to surpass Africa as the world’s poorest region in the foreseeable future Is the Pacific not sinking but being sunk?

Corruption in many Pacific countries appears endemic, the Pacific has the world’s fastest growth rate of HIV infection and the Pacific is predicted to surpass Africa as the world’s poorest region in the foreseeable future Is the Pacific not sinking but being sunk?

As part of a new series on elephant conservation we’d like to hear about your experiences with the world’s largest land mammal

Over the next year we’re going to be covering the plight of elephants around the world. The numbers of these beautiful animals – now our largest land mammal – have been in steep decline for a century and now face more serious challenges than ever, due to poaching, habitat destruction, and conflict with man.

Please help with our coverage by getting in touch and telling us your own stories, encounters and campaigns. Are you a wildlife campaigner in Asia? A grassroots activist in Africa? Whoever you are, we want to hear from you about your own encounters with elephants.

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Demonstrators focus on driving up policing costs as anti-bovine TB programme expanded across south-west England

Protesters against the badger cull in England have said they plan to change tactics by undertaking direct action to drive up policing costs, following reports of an expansion of culling to new areas.

The BBC has reported that the cull will be extended to five new areas in south-west England – south Devon, north Devon, north Cornwall, west Dorset and south Herefordshire – where badger shooting will begin in early September as part of government efforts to eradicate bovine TB.

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