Arctic heating races ahead of worst-case estimates

September 2, 2020 / activist360 / Leave a comment

Arctic heating is happening far faster than anybody had anticipated. And the ice record suggests this has happened before.

September 2, 2020 by Tim Radford, Climate News Network (CC BY-ND 4.0)

*Svalbard, in whose waters temperatures have risen at 1.5°C every decade for the last 40 years. Image: By Vince Gx on Unsplash*

LONDON, 2 September, 2020 – An international team of scientists brings bad news about Arctic heating: the polar ocean is warming not only faster than anybody predicted, it is getting hotter at a rate faster than even the worst case climate scenario predictions have so far foreseen.

Such dramatic rises in Arctic temperatures have been recorded before, but only during the last Ice Age. Evidence from the Greenland ice cores suggests that temperatures rose by 10°C or even 12°C, over a period of between 40 years and a century, between 120,000 years and 11,000 years ago.

“We have been clearly underestimating the rate of temperature increases in the atmosphere nearest to the sea level, which has ultimately caused sea ice to disappear faster than we had anticipated,” said Jens Hesselbjerg Christensen, a physicist at the University of Copenhagen in Denmark, one of 16 scientists who report in the journal Nature Climate Change on a new analysis of 40 years of data from the Arctic region.

They found that, on average, the Arctic has been warming at the rate of 1°C per decade for the last four decades. Around Norway’s Svalbard archipelago, temperatures rose even faster, at 1.5°C every 10 years.

We have been clearly underestimating the rate of temperature increases in the atmosphere nearest to the sea level, which has ultimately caused sea ice to disappear faster than we had anticipated.”
—Jens Hesselbjerg Christensen, Physicist, University of Copenhagen

During the last two centuries, as atmospheric levels of carbon dioxide climbed from an average of around 285 parts per million to more than 400ppm, so the global average temperature of the planet rose: by a fraction more than 1°C.

The latest study is a reminder that temperatures in the Arctic are rising far faster than that. And the news is hardly a shock: within the past few weeks, separate teams of researchers, reporting to other journals, have warned that Greenland – the biggest single reservoir of ice in the northern hemisphere – is melting faster than ever; more alarmingly, its icecap is losing mass at a rate that suggests the loss could become irreversible.

Researchers have also confirmed that the average planetary temperature continues to rise inexorably, that the Arctic Ocean could be free of ice in summer as early as 2035, and that the climate scientists’ “worst case” scenarios are no longer to be regarded as a warning of what could happen: the evidence is that what is happening now already matches the climate forecaster’s worst case. The latest finding implicitly and explicitly supports this flurry of ominous observation.

“We have looked at the climate models analysed and assessed by the UN Climate Panel,” said Professor Christensen. “Only those models based on the worst case scenario, with the highest carbon dioxide emissions, come close to what our temperature measurements show over the past 40 years, from 1979 to today.” – Climate News Network

Annual Planetary Temperature Continues to Rise

August 17, 2020 / activist360 / Leave a comment

More than 500 scientists from 61 countries have again measured the annual planetary temperature. The diagnosis is not good.

*Wildfire strikes Bandipur national park, one of India’s prime tiger reserves. Image: By NaveenNkadalaveni, via Wikimedia Commons*

August 17, 2020 by Tim Radford, Climate News Network (CC BY-ND 4.0)

LONDON, 17 August, 2020 – Despite global promises to act on climate change, the Earth continues to warm. The annual planetary temperature confirms that the last 10 years were on average 0.2°C warmer than the first 10 years of this century. And each decade since 1980 has been warmer than the decade that preceded it.

The year 2019 was also one of the three warmest years since formal temperature records began in the 19th century. The only warmer years – in some datasets but not all – were 2016 and 2015. And all the years since 2013 have been warmer than all other years in the last 170.

The link with fossil fuel combustion remains unequivocal: carbon dioxide levels in the atmosphere increased by 2.5 parts per million (ppm) in 2019 alone. These now stand at 409 ppm. The global average for most of human history has hovered around 285 ppm.

Two more greenhouse gases – nitrous oxide and methane, both of them more short-lived – also increased measurably.

This millennium has been warmer than any comparable period since the Industrial Revolution.”
—Robert Dunn, of the UK Met Office

The study, in the Bulletin of the American Meteorological Society, is a sobering chronicle of the impact of climate change in the decade 2010-2019 and the year 2019 itself. It is the 30th such report, it is signed by 528 experts from 61 countries, and it is a catalogue of unwelcome records achieved and uncomfortable extremes surpassed.

July 2019 was the hottest month on record. Record high temperatures were measured in more than a dozen nations across Africa, Europe, Asia and the Caribbean. In North America, Alaska scored its hottest year on record.

The Arctic as a whole was warmer than in any year except 2016. Australia achieved a new nationally average daily temperature high of 41.9°C on 18 December, breaking the previous 2013 record by 1.6°C. But even Belgium and the Netherlands saw temperatures higher than 40°C.

For the 32nd consecutive year, the world’s alpine glaciers continued to get smaller and retreat further uphill. For the first time on record in inland Alaska, when measured at 26 sites, the active layer of permafrost failed to freeze completely. In September, sea ice around the Arctic reached a minimum that tied for the second lowest in the 41 years of satellite records.

Catalogue of Extremes

Global sea levels set a new high for the eighth consecutive year and are now 87.6mm higher than the 1993 average, when satellite records began. At a depth of 700 metres, ocean temperatures reached new records, and the sea surface temperatures on average were the highest since 2016.

Drought conditions led to catastrophic wildfires in Australia, in Indonesia, Siberia and in the southern Amazon forests of Bolivia, Brazil and Peru. And around the equator, meteorologists catalogued 96 named tropical storms: the average for 1981 to 2010 was 82. In the North Atlantic, just one storm, Hurricane Dorian, killed 70 people and caused $3.4bn (£2.6bn) in damage in the Bahamas.

“This millennium has been warmer than any comparable period since the Industrial Revolution. A number of extreme events, such as wildfires, heatwaves and droughts, have at least part of their root linked to the rise in global temperature,” said Robert Dunn, of the UK Met Office, one of the contributors.

“And of course the rise in global temperature is linked to another climate indicator, the ongoing rise in emissions in greenhouse gases, notably carbon dioxide, nitrous oxide and methane.” – Climate News Network

End of Arctic Sea Ice by 2035 Possible, Study Finds

August 11, 2020 / activist360 / Leave a comment

August 11th, 2020, by Alex Kirby (CC BY-ND 4.0)

How soon will the northern polar ocean be ice-free? New research expects the end of Arctic sea ice by 2035.

LONDON, 11 August, 2020 − The temperature of the Arctic matters to the entire world: it helps to keep the global climate fairly cool. Scientists now say that by 2035 there could be an end to Arctic sea ice.

*Photo by Willian Justen de Vasconcellos on Unsplash*

The northern polar ocean’s sea ice is a crucial element in the Earth system: because it is highly reflective, it sends solar radiation back out into space. Once it’s melted, there’s no longer any protection for the darker water and rock beneath, and nothing to prevent them absorbing the incoming heat.

High temperatures in the Arctic during the last interglacial – the warm period around 127,000 years ago – have puzzled scientists for decades.

Now the UK Met Office’s Hadley Centre climate model has enabled an international research team to compare Arctic sea ice conditions during the last interglacial with the present day. Their findings are important for improving predictions of future sea ice change.

What is striking about the latest research is the date it suggests for a possible total melt − 2035. Many studies have thought a mid-century crisis likely, with another even carefully specifying 2044 as the year to watch. So a breathing space of only 15 years may surprise some experts.

“The prospect of loss of sea ice by 2035 should really be focussing all our minds on achieving a low-carbon world as soon as humanly feasible”

During spring and early summer shallow pools of water form on the surface of the Arctic sea ice. These “melt ponds” help to determine how much sunlight is absorbed by the ice and how much is reflected back into space. The new Hadley Centre model is the UK’s most advanced physical representation of the Earth’s climate and a critical tool for climate research, and it incorporates sea ice and melt ponds.

The researchers report their findings in the journal Nature Climate Change. Using the model to look at Arctic sea ice during the last interglacial, they concluded that the impact of intense springtime sunshine created many melt ponds, which played a crucial role in sea ice melt. A simulation of the future using the same model indicates that the Arctic may become sea ice-free by 2035.

The joint lead author of the team is Dr Maria Vittoria Guarino, an earth system modeller at the British Antarctic Survey (BAS) in Cambridge. She says: “High temperatures in the Arctic have puzzled scientists for decades. Unravelling this mystery was technically and scientifically challenging. For the first time, we can begin to see how the Arctic became sea ice-free during the last interglacial.

“The advances made in climate modelling mean that we can create a more accurate simulation of the Earth’s past climate which, in turn, gives us greater confidence in model predictions for the future.”

Dr Louise Sime, the group head of the palaeoclimate group and joint lead author at BAS, says: “We know the Arctic is undergoing significant changes as our planet warms. By understanding what happened during Earth’s last warm period we are in a better position to understand what will happen in the future.

Melt ponds crucial

“The prospect of loss of sea ice by 2035 should really be focussing all our minds on achieving a low-carbon world as soon as humanly feasible.”

Dr David Schroeder from the University of Reading, UK, who co-led the implementation of the melt pond scheme in the climate model, says: “This shows just how important sea ice processes like melt ponds are in the Arctic, and why it is crucial that they are incorporated into climate models.”

The extent of the areas sea ice covers varies between summer and winter. If more solar energy is absorbed at the surface, and temperatures rise further, a cycle of warming and melting occurs during summer months.

When the ice forms, the ocean water beneath becomes saltier and denser than the surrounding ocean. Saltier water sinks and moves along the ocean bottom towards the equator, while warm water from mid-depths to the surface travels from the equator towards the poles.

Scientists refer to this process as the ocean’s global “conveyor-belt”. Changes to the volume of sea ice can disrupt normal ocean circulation, with consequences for global climate. − Climate News Network