05/10/2020

The Arctic Hasn’t Been This Warm For 3 Million Years – And That Foreshadows Big Changes For The Rest Of The Planet

The Conversation -  | 

Ice floe drifting in Svalbard, Norway. Sven-Erik Arndt/Arterra/Universal Images Group via Getty Images

Authors
  • Julie Brigham-Grette is Professor of Geosciences, University of Massachusetts Amherst
  •  is Associate Professor of Geosciences, University of Massachusetts Amherst
Every year, sea ice cover in the Arctic Ocean shrinks to a low point in mid-September.

This year it measures just 1.44 million square miles (3.74 million square kilometers) – the second-lowest value in the 42 years since satellites began taking measurements.

The ice today covers only 50% of the area it covered 40 years ago in late summer.

As the Intergovernmental Panel on Climate Change has shown, carbon dioxide levels in the atmosphere are higher than at any time in human history. The last time that atmospheric CO2 concentrations reached today’s level – about 412 parts per million – was 3 million years ago, during the Pliocene Epoch.

This year’s minimum ice extent is the lowest in the 42-year-old satellite record except for 2012, reinforcing a long-term downward trend in Arctic ice cover. Each of the past four decades averages successively less summer sea ice. NSIDC

As geoscientists who study the evolution of Earth’s climate and how it creates conditions for life, we see evolving conditions in the Arctic as an indicator of how climate change could transform the planet. If global greenhouse gas emissions continue to rise, they could return the Earth to Pliocene conditions, with higher sea levels, shifted weather patterns and altered conditions in both the natural world and human societies.

The Pliocene Arctic

We are part of a team of scientists who analyzed sediment cores from Lake El’gygytgyn in northeast Russia in 2013 to understand the Arctic’s climate under higher atmospheric carbon dioxide levels. Fossil pollen preserved in these cores shows that the Pliocene Arctic was very different from its current state.

Today the Arctic is a treeless plain with only sparse tundra vegetation, such as grasses, sedges and a few flowering plants. In contrast, the Russian sediment cores contained pollen from trees such as larch, spruce, fir and hemlock. This shows that boreal forests, which today end hundreds of miles farther south and west in Russia and at the Arctic Circle in Alaska, once reached all the way to the Arctic Ocean across much of Arctic Russia and North America.

Because the Arctic was much warmer in the Pliocene, the Greenland Ice Sheet did not exist. Small glaciers along Greenland’s mountainous eastern coast were among the few places with year-round ice in the Arctic. The Pliocene Earth had ice only at one end – in Antarctica – and that ice was less extensive and more susceptible to melting.

Boreal forest near Lake Baikal in Russia. Three million years ago these forests extended hundreds of miles farther north than they reach today. Christophe Meneboeuf/Wikipedia, CC BY-SA

Because the oceans were warmer and there were no large ice sheets in the Northern Hemisphere, sea levels were 30 to 50 feet (9 to 15 meters) higher around the globe than they are today. Coastlines were far inland from their current locations.

The areas that are now California’s Central Valley, the Florida Peninsula and the Gulf Coast all were underwater. So was the land where major coastal cities like New York, Miami, Los Angeles, Houston and Seattle stand.

Warmer winters across what is now the western U.S. reduced snowpack, which these days supplies much of the region’s water. Today’s Midwest and Great Plains were so much warmer and dryer that it would have been impossible to grow corn or wheat there.

Why was there so much CO2 in the Pliocene?

How did CO2 concentrations during the Pliocene reach levels similar to today’s? Humans would not appear on Earth for at least another million years, and our use of fossil fuels is even more recent.

The answer is that some natural processes that have occurred on Earth throughout its history release CO2 to the atmosphere, while others consume it.

The main system that keeps these dynamics in balance and controls Earth’s climate is a natural global thermostat, regulated by rocks that chemically react with CO2 and pull it out of the atmosphere.

The Greenhouse Effect leads to increases in surface temperatures and, in some places, rainfall. Together these accelerate silicate rock weathering. Faster weathering in turn removes more CO2 from the atmosphere (yellow arrow). The strength of the Greenhouse Effect relies on atmospheric CO2 levels. Gretashum/Wikipedia

In soils, certain rocks continually break down into new materials in reactions that consume CO2. These reactions tend to speed up when temperatures and rainfall are higher – exactly the climate conditions that occur when atmospheric greenhouse gas concentrations rise.

But this thermostat has a built-in control. When CO2 and temperatures increase and rock weathering accelerates, it pulls more CO2 from the atmosphere. If CO2 begins to fall, temperatures cool and rock weathering slows globally, pulling out less CO2.

Rock weathering reactions also can work faster where soil contains lots of newly exposed mineral surfaces. Examples include areas with high erosion or periods when Earth’s tectonic processes pushed land upward, creating major mountain chains with steep slopes.

The rock weathering thermostat operates at a geologically slow pace. For example, at the end of the Age of Dinosaurs about 65 million years ago, scientists estimate that atmospheric CO2 levels were between 2,000 and 4,000 parts per million. It took over 50 million years to reduce them naturally to around 400 parts per million in the Pliocene.

Because natural changes in CO2 levels happened very slowly, cyclic shifts in Earth’s climate system were also very slow. Ecosystems had millions of years to adapt, adjust and slowly respond to changing climates.


Summer heat waves are altering northern Siberia, thawing permafrost and creating conditions for large-scale wildfires.

A Pliocene-like future?

Today human activities are overwhelming the natural processes that pull CO2 out of the atmosphere. At the dawn of the Industrial Era in 1750, atmospheric CO2 stood at about 280 parts per million. It has taken humans only 200 years to completely reverse the trajectory begun 50 million years ago and return the planet to CO2 levels not experienced for millions of years.

Most of that shift has happened since World War II. Yearly increases of 2-3 parts per million now are common. And in response, the Earth is warming at a fast pace. Since roughly 1880 the planet has warmed by 1 degree Celsius (2 degrees Fahrenheit) – many times faster than any warming episode in the past 65 million years of Earth’s history.

In the Arctic, losses of reflective snow and ice cover have amplified this warming to +5 C (9 F). As a result, summertime Arctic sea ice coverage is trending lower and lower. Scientists project that the Arctic will be completely ice-free in summer within the next two decades.

This isn’t the only evidence of drastic Arctic warming. Scientists have recorded extreme summer melt rates across the Greenland Ice Sheet. In early August, Canada’s last remaining ice shelf, in the territory of Nunavut, collapsed into the sea. Parts of Arctic Siberia and Svalbard, a group of Norwegian islands in the Arctic Ocean, reached record-shattering high temperatures this summer.

Coastal cities, agricultural breadbasket regions and water supplies for many communities all will be radically different if this planet returns to a Pliocene CO2 world. This future is not inevitable – but avoiding it will require big steps now to decrease fossil fuel use and turn down Earth’s thermostat.

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As Afghans Count Cost Of Deadly Floods, Officials Warn Of Worse To Come

Reuters - Shadi Khan Saif

As the climate heats up, war-weary communities need more help to prepare for the growing threat of droughts and floods, and to protect their fragile environment

People search for victims after floods in Charikar, capital of Parwan province, Afghanistan August 27, 2020. REUTERS/Mohammad Ismail 

CHARIKAR, Afghanistan - Grocer Aziz Ullah took in his brother's three children after he was killed by devastating flash floods in late August which also destroyed Ullah's shop in the northern Afghan city of Charikar.

"These poor orphans have lost their parents and have nowhere to go," said the father-of-five, 59. "How am I going to look after their needs? Only God knows."

In the once-bustling provincial capital of Parwan, where nearly 160 people died, residents are trying to repair their shattered properties, while still grieving for relatives.

The north and east of the country are struggling to recover from the effects of the heavy downpours that claimed more than 200 lives, mostly women and children, across 13 provinces, as officials warn climate change could bring more such disasters.

In August, torrential rains swept off the majestic Hindu Kush mountains and through the valleys of Parwan, washing away hundreds of homes.

When Afghan President Ashraf Ghani visited the area in early September, he noted that 80% of natural floodwater channels had been turned into residential areas, increasing the loss of life.

He ordered Charikar's administration to clear the flood pathways, resettle people now living there, and produce a new development master plan for the city.

Thousands of hectares of farmland were also damaged and livestock perished in the floods that caught local communities off-guard.

An Afghan man stands at his house after floods in Charikar, capital of Parwan province, Afghanistan August 27, 2020. REUTERS/Mohammad Ismail



Tiny Emissions

Rohullah Amin, deputy head of the National Environmental Protection Agency (NEPA), set up in 2010, warned of far worse impacts from rising temperatures and erratic weather in the coming years if climate change "is not taken seriously locally and internationally".

"The developed world needs to take responsibility as we have barely contributed to climate change, but are losing so many lives due to it," he told the Thomson Reuters Foundation.

With very little industry of its own, Afghanistan accounts for far less than 1% of global greenhouse gas emissions.

In a report submitted to the United Nations in 2017, the NEPA said that since 1950, Afghanistan's mean annual temperature had increased significantly by 1.8 degrees Celsius, while spring rainfall - important for crops - had decreased by up to a third.

Amin called for greater support from wealthy, high-emitting countries for his war-ravaged nation that, despite its tiny role in heating up the planet, is on the receiving end of the wild weather being intensified by global warming.

Afghanistan ranks among the countries most at risk of - and least prepared for - climate-linked threats ranging from food insecurity to disease outbreaks, according to an index compiled by the Notre Dame Global Adaptation Initiative.

U.N. agencies says droughts are likely to become the norm in Afghanistan by 2030, leading to land degradation and desertification, affecting more than a third of its 38 million people.

Projections by the NEPA suggest rising temperatures will lead to reduced spring rainfall and higher evapotranspiration, together with more frequent extreme events such as droughts, floods, landslides and avalanches.

But preparing people for that, and encouraging them to take precautions, will not be easy, said Mohammad Iqbal, director of public awareness at the NEPA.

"Even after these floods, it is hard to convince the locals, especially the poor farmers - who are suffering the most - that climate change is real and they need to adapt to this new reality," he told the Thomson Reuters Foundation.

The government has launched programmes to raise awareness about climate impacts and encourage better protection of the country's fragile environment, with the help of local community and religious leaders.

Under a new national climate action plan developed by the NEPA, now pending cabinet approval, it also aims to move gradually towards clean energy, cut back on low-grade coal for heating in its harsh winter, and launch a reforestation drive.

People search for victims after floods in Charikar, capital of Parwan province, Afghanistan August 27, 2020. REUTERS/Mohammad Ismail

War-Weary

But the impacts of climate change are already exacerbating the consequences of long years of war.

Spells of drought followed by untimely torrential rains - coupled with political insecurity - displaced more than 500,000 Afghans last year alone, according to the United Nations Office for the Coordination of Humanitarian Affairs.

Amin, who leads the NEPA's climate change directorate, warned the recent floods should be taken as a "grim reminder and alarm calls" for what the future may have in store.

Glaciers are melting rapidly, compounding the threat of flash floods, which can severely damage crop yields, he added.

The NEPA estimates that well over half of households across Afghanistan depend on farming and livestock-keeping for their main source of income.

The August floods hit the northern, eastern and central highlands, where rain-fed farming and pastoralism are common, hampering households' ability to produce enough food and income to meet their basic needs, NEPA officials said.

Environmentalist Sayed Montazer Shah, a former adviser at the agriculture ministry, said the government and the international community had neglected Afghanistan's "environmental emergency", with the spotlight on its recently rejuvenated but fragile peace process.

Government and Taliban negotiators have been meeting in Doha since Sept. 12, hoping to agree on a ceasefire and a power-sharing deal. But they have been bogged down in the principles and procedures for the talks.

Shah said the country's ongoing conflict also had inflicted harm on its ecosystems, which in turn could add more deaths to the toll from violence.

"The forest cover is fast depleting, with trees in the jungles - particularly in the areas held by the (Taliban) insurgents - being cut ruthlessly at an alarming rate," Shah said, noting militants are likely working hand in hand with illegal loggers to make money.

The 2017 NEPA report said Afghanistan's forests were severely damaged as a result of decades of deforestation, over-harvesting, mismanagement and drought - and covered just 1.5-2% of the country.

In mountainous areas especially, deforestation can lead to soil erosion, hiking the risks of deadly landslides and floods.

Amin of the NEPA said he hoped the renewed push for peace would take a holistic view of the multiple risks facing the country – including its environment.

"Our sincere hope and aspiration is that all sides embrace peace and realise the common threat of climate change," he said.

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Global Heating Warming Up 'Nights Faster Than Days'

The Guardian - 

Effect seen across much of world will have profound consequences, warn scientists

The changes will impact many animal species and their ability to adapt to the climate crisis, research shows. Photograph: NiseriN/Getty/iStockPhoto

The climate crisis is heating up nights faster than days in many parts of the world, according to the first worldwide assessment of how global heating is differently affecting days and nights.

The findings have “profound consequences” for wildlife and their ability to adapt to the climate emergency, the researchers said, and for the ability of people to cool off at night during dangerous heatwaves.

The scientists compared the rises in daytime and night-time temperatures over the 35 years up to 2017. Global heating is increasing both, but they found that over more than half of the world’s land there was a difference of at least 0.25C between the day and night rises.

In two-thirds of those places, nights were warming faster than the days, particularly in Europe, west Africa, western South America and central Asia. But in some places – southern US, Mexico and the Middle East – days were warming faster.

The changes are the result of global heating causing changes to clouds. Where cloud cover increases, sunlight is blocked during the day but the clouds retain more heat and humidity at night, like a blanket.

This leads to nights getting increasingly hotter compared with days. Where cloud cover is decreasing, mostly in regions that are already dry, there is more sunlight during the day, which pushes temperatures up more rapidly.

Ecosystems have evolved as fine balances between species and many biological activities, such as feeding, occur at specific times of day. So the asymmetric changes between night and day temperatures in many parts of the world “will have profound consequences for the species inhabiting those regions and their ability to adapt in the face of the changing climate”, the scientists said.

The research is published in the journal Global Change Biology.

Daniel Cox, a research fellow at the University of Exeter and leader of the study, said: “We demonstrated that greater night-time warming is associated with the climate becoming wetter, and this has been shown to have important consequences for plant growth and how species, such as insects and mammals, interact.

“Species that are only active at night or during the day will be particularly affected.”

Wildlife is already in deep trouble, with global populations having plunged by an average of 68% since 1970.

Some changes caused by temperature rises have previously been recorded by other scientists. The predation of aphid insects and the hunting by African wild dogs are increasing at night, potentially upsetting food chains.

In the US, night-time temperatures have increased at twice the rate of daytime temperatures, exacerbating the dangers of heatwaves that already kill more Americans than any other natural disaster.

Cox’s team also looked at vegetation growth and found that it was reduced where nights were getting warmer faster than days, probably because the increased cloud cover blocks the sun.

However, plant growth was also reduced in places where the days warmed more, as there were fewer clouds and less rainfall. Both effects are likely to cut crop yields and, for example, reduce nectar and pollen production that many insects rely on.

Mark Wright, the director of science at WWF-UK, said: “While it’s too early to determine the impact on any individual species, this potentially significant finding provides further evidence of the imbalances being forced on nature by humankind.

“We know we need to take urgent action to halt and reverse humanity’s impact on nature, including rapid and deep cuts to greenhouse gas emissions.”

Overviews of the climate crisis often focus on average global temperature rises, but the impacts vary widely around the world. Previous climate studies have shown that some areas, such as the Arctic and Himalayan plateau, are heating up much faster than elsewhere and that spring is coming earlier and frosts and snow are becoming less common.

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