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Lakes Are Shrinking | Earth Wise

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A study by the University of Colorado Boulder has found that more than half of the world’s largest lakes have shrunk over the last three decades.  This is a very big problem because about one-quarter of the Earth’s population lives in the basin of a drying lake.  People depend on lakes for drinking water and irrigation and lakes are central to the survival of local ecosystems as well as migrating birds.  Lakes cover only about 3% of the planet, but they hold nearly 90% of the liquid surface freshwater.

The study used satellite observations from 1992 to 2020 to estimate the area and water levels of nearly 2,000 freshwater bodies.  These account for 96% of Earth’s total natural lake storage and 83% of that in man-made reservoirs.  About 53% of the world’s lakes have clearly shrunk, while only 22% have gained water.  The study estimates that about 160 trillion gallons of water has been lost over the 28-year period.  That’s about 17 times the maximum capacity of Lake Mead, the largest reservoir in the United States.

Many of the world’s most significant lakes have been shrinking. The dramatic declines in Lake Mead have been headline news for years.  The Caspian Sea, which is the world’s largest inland body of water – has long been declining.

The main causes of the decline in natural lakes are climate change and human consumption.  Reservoirs face an additional major problem of sediment buildup which reduces their storage capacity and diminishes their benefits of water supply, flood control, and hydropower.

Lake loss is a big problem.

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More than half of the world’s largest lakes are drying up

Photo, posted April 10, 2018, courtesy of Ninara via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Missing Antarctic Sea Ice | Earth Wise

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It is summer here in the United States, but it is winter in Antarctica.  Antarctic sea ice is water that forms and melts entirely in the ocean and it has a pattern of growth and reduction that has been monitored by satellites for the past 44 years.  The area of sea ice that surrounds the continent of Antarctica is known as the sea ice ‘extent’ and it had been quite stable for much of those years.

In 2016, the sea ice extent began to decline.  Since then, there have been several record summer lows with both the summers of 2021/22 and 2022/23 setting new minimum records.

This August, the deviation from all previous records intensified.  This winter’s sea ice extent is over 900,000 square miles below the long-term average, an area about the size of Greenland or, for example, Texas and Alaska combined.

Climate models have long predicted that Antarctic sea ice would reduce as a result of global warming but the current change to sea-ice extent is so dramatic that it is difficult to explain.  Sea ice extent is affected by multiple factors including the El Niño Southern Oscillation, the strength of the southern hemisphere jet stream, and regional low-pressure systems.  The warming climate is certainly the overall force that is changing Antarctic sea ice extent over time.

Antarctic sea ice extent is important because it covers a vast area of the dark Southern Sea with a bright white surface that reflects the sun’s energy back into space, helping to reduce temperatures at the pole and protecting glaciers and polar ice sheets. 

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The mystery of the missing Antarctic sea ice

Photo, posted November 7, 2016, courtesy of Rob Oo via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Dangers Of Melting Glaciers | Earth Wise

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Some of most dramatic evidence that the Earth’s climate is warming is the retreat and even disappearance of mountain glaciers around the world.  2022 was the 35th year in a row that glaciers tracked by the World Glacier Monitoring Service lost rather than gained ice.  Glaciers gain mass through snowfall and lose mass through melting and sublimation (water evaporating directly from solid ice.)  Some glaciers that terminate in lakes or the ocean lose mass through iceberg calving.

In the warming climate, glaciers retreat and meltwater collects at the front of the glacier forming a lake.  Such lakes can suddenly burst and create a fast-flowing Glacier Lake Outburst Flood that can spread over a large distance from the original site – in some cases over 70 miles.  These floods can damage property, infrastructure, and agricultural land and can also be deadly.

The number of glacial lakes has grown rapidly since 1990 as a result of climate change.  According to research by an international team of scientists led by Newcastle University in the UK, the number of people living in glacial lake catchments has increased significantly.

According to the study, 15 million people live within 30 miles of a glacial lake.  The highest danger is in High Mountain Asia – which encompasses the Tibetan Plateau.  That area, which spans from Kyrgyzstan to parts of China, has 9.3 million people potentially at risk.  India and Pakistan have around 5 million exposed people.

Detailed analysis shows that it is not the areas with the largest number or most rapidly growing lakes that are most dangerous.  It is the number of people in proximity to the lakes and their ability to cope with potential floods.

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Glacial flooding threatens millions globally

Photo, posted February 12, 2022, courtesy of David Stanley via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Progress Towards Carbon-Free Power | Earth Wise

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Climate change has driven countries, states, utilities, and corporations to set goals to eliminate power-sector carbon emissions.  So far, 17 U.S. states plus Washington, D.C. and Puerto Rico have adopted laws or executive orders to achieve 100% carbon-free electricity over the next couple of decades.  Forty-six U.S. utilities have pledged to go carbon-free no later than 2050.   Adding these together, these government and industry goals cover about half of the U.S. population and economy.

New research from the Lawrence Berkeley National Laboratory has analyzed historical trends to determine how much progress the power sector has already made in reducing emissions.  The study focused on the 2005 Annual Energy Outlook from the U.S. government’s Energy Information Administration.

If the previous growth in emissions had continued from 2005 to 2020, annual CO2 emissions would have risen from 2,400 to 3,000 million metric tons.  But actual 2020 emissions fell to only 1,450 metric tons.  So, by this metric, the U.S. power sector cut emission by 52% below projected levels.

According to the study, total consumer electricity costs were 18% lower than projected values, but meanwhile, the number of jobs in electricity generation was 29% higher. 

Among the driving forces for these trends were wind and solar power dramatically outperforming earlier expectations, delivering 13 times more generation in 2020 than projected. 

The study shows that dramatic changes in emissions are possible over a 15-year span, but much has to happen over the next 15 years to ensure the progress required to meet the ambitious goals set for emissions reductions.

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U.S. Power Sector is Halfway to Zero Carbon Emissions

Photo, posted April 18, 2020, courtesy of Roman Ranniew via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Renewables Taking Over In Britain

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A year-and-a-half ago, we reported on the steep decline in the use of coal in Britain, including the conversion of the giant Drax Power Station from burning coal to running on wood chips.  Since then, Britain has been steadily moving away from fossil fuels and towards renewable energy sources.  The transformation is being driven by a surge in offshore wind farms currently under construction or about to begin operating.  Britain is in the process of adding over 6 GW of offshore wind to its current total of 8 GW.  Renewables generated one-third of the UK’s electricity last year, and half of that came from wind power. 

In 2018, coal- and gas-fired power stations generated about 131 terawatt-hours of electricity in Britain.  Renewable energy plants – including wind, solar, biomass, and hydropower – produced about 96 terawatt-hours.  Based on the new projects coming online, renewable sources could generate 121 TWh by 2020 and fossil fuel plants are likely to fall to 105.6 TWh as more coal plants are retired.  Thus, within the next year or so, renewables in Britain are likely to surpass fossil fuels in electricity generation.

The transformation in Britain has been rapid and dramatic.  In 1974, the country generated 80% of its electricity using coal.  By 2016, that number had dropped to 9%.  Last April, the British power grid went three days in a row without burning any coal.  The UK is expected to shut down its remaining coal plants by 2025, if not sooner. 

At the same time, Britain’s renewable energy capacity has more than quadrupled since 2010, jumping from 21 TWh that year to 96 TWh last year.  Britain’s energy mix is changing fast and getting significantly cleaner every year.

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Renewables Could Surpass Fossil Fuels in Britain by 2020

Photo, posted August 2, 2008, courtesy of Richard Allaway via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Cooling Cities With White Roofs

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The phenomenon of urban heat islands has been well known since the 19th century.  The materials from which city buildings and roads are made reflect much less solar radiation and absorb more of it than the vegetation they have replaced.  The absorbed energy is then radiated in the form of heat into the surrounding air making cities warmer.

[Read more…] about Cooling Cities With White Roofs

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