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Cooling Down Urban Heat Islands

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Researchers have known about and studied the urban heat island effect for quite some time.  Since large cities began to emerge in the 19th century, it has been understood that various aspects of the urban environment lead to warmer temperatures than the surrounding countryside.

Researchers led by a group at Portland State University in Oregon have been utilizing a new way of studying the urban heat island effect.  They have used citizen science volunteers in 24 cities around the world to map temperatures in the cities at ground level in great detail using mobile sensors attached to slow-moving vehicles.  Previous studies have used data from satellite or stationary sensors.  They have learned that the urban heat island effect is more complicated, more varied, and subtler than the earlier data indicated.

They found that there are six things that affect urban heat. Three are living — the volume of the tree canopy, the height of the tree canopy, and the ground level vegetation. Three are human-built — the volume of buildings, the difference in building heights, and the coloring of the buildings.

Buildings can have both negative and positive effects. Tall buildings that cast shade actually lower relative afternoon temperatures, while densely packed shorter buildings, like the big-box stores in suburban areas, lead to hotter afternoon temperatures. The studies show that increasing the difference in building heights in an area creates more air circulation, which has a cooling effect.

The study also showed that urban heat is a social justice issue.  Lower-income neighborhoods largely barren of trees have considerably higher temperatures than more affluent, tree-shaded areas.

Such detailed research can be used to guide decisions in urban planning with regard to trees, building heights, and the color and type of surfaces in our urban spaces.

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Can We Turn Down the Temperature on Urban Heat Islands?

Photo, posted July 21, 2009, courtesy of Daniel Dionne via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Climate Change Is Not Natural

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It has been the overwhelming consensus of the scientific community for a long time that human activity and other external factors are responsible for the continuing rise in global temperature.  Despite this widespread agreement, there have been those who argue that natural ocean cycles might be influencing global warming over the course of multiple decades.

A new study, published in the Journal of Climate, provides an answer to the question of how much influence natural cycles might have, and that answer is very little to none.

The study looked at observed ocean and land temperature data since 1850 and, apart from human-induced factors such as greenhouse gas concentrations, took into account other occurrences such as volcanic eruptions, solar activity, and air pollution peaks.  The findings demonstrated that slow-acting ocean cycles do not explain the long-term changes in global temperatures.

Based on the study, the researchers can state with confidence that human factors like greenhouse gas emissions and particulate pollution, along with year-to-year changes caused by natural phenomena like volcanic eruptions or El Niño, are sufficient to explain virtually all the long-term changes in temperature.  The idea that the oceans could have been driving the climate either in a colder or warmer direction for multiple decades in the past and therefore will do so in the future is unlikely to be correct.

A number of previous studies have compared flawed observations with flawed modeling results to claim that naturally-occurring ocean cycles have played a large role in global temperatures.  The new study shows that such cycles have little influence on the climate.  Reducing greenhouse gas emissions is really what we need to do.

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Global temperature change attributable to external factors, confirms new study

Photo, posted November 13, 2007, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Climate Change And Dolphins

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We don’t think of heatwaves as something that affects the ocean, but increasingly, as the planet warms, there have been instances where ocean water temperatures become much higher than normal for extended periods of time.  There has been much discussion of this phenomenon with regard to coral reefs where the catastrophic rise in coral bleaching events has been the result.

Recently, a study at the University of Zurich looked at the effects of ocean heatwaves on marine life higher in the food chain.  They studied the well-known dolphin population in Shark Bay, Western Australia.

In early 2011, a heatwave caused water temperatures in Shark Bay to rise more than 4 degrees above the annual average for an extended period.  This led to a substantial loss of seagrass, which is a driving factor in the Shark Bay ecosystem.

The researchers investigated how this environmental damage affected survival and reproduction of dolphins, using long-term data on hundreds of animals collected over a ten-year period from 2007 to 2017.

Their analysis showed that dolphins’ survival rate dropped by 12% and female dolphins were giving birth to fewer calves.  That phenomenon that began in 2011 lasted at least until 2017.

The researchers were surprised by the extent and the duration of the influence of the heatwave, especially the fact that the reproductive rate of dolphins had not returned to normal even after 6 years.

This study shows for the first time that marine heatwaves not only affect organisms at the lower levels of the food chain, but also might have considerable long-term consequences for the animals at the top, such as dolphins.

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Climate change is a threat to dolphins’ survival

Photo, posted December 14, 2014, courtesy of Ed Dunens via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Forecasting A Bad Year For Carbon

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Carbon dioxide levels in the atmosphere are higher than they have been for hundreds of thousands of years, and they continue to grow.  The United Kingdom’s national meteorological service – known as the Met Office – issues annual predictions of global CO2 levels based in part on readings taken at the Mauna Loa observatory in Hawaii.  Their forecast for this year is that there will be one of the largest rises in atmospheric carbon-dioxide concentration in the 62 years of measurements at Mauna Loa.

Since 1958, there has been a 30% increase in the concentration of carbon dioxide in the atmosphere.  This has been caused by emissions from fossil fuels, deforestation and cement production.  The increase would actually have been even larger if it were not for natural carbon sinks in the form of various ecosystems that soak up some of the excess CO2.

Weather patterns linked to year-by-year swings in Pacific Ocean temperatures are known to affect the uptake of carbon dioxide by land ecosystems.  In years with a warmer tropical Pacific – such as El Niño years – many regions become warmer and drier, which limits the ability of plants to grow and to absorb CO2 .  The opposite happens when the Pacific is cool, as was the case last year.

The Met Office predicts that the contribution of natural carbon sinks will be relatively weak, so the impact of human-caused emissions will be larger than last year.  The predicted rise in atmospheric CO2 is 2.75 parts-per-million, which is among the highest rises on record.  The forecast for the average carbon dioxide concentration is 411 ppm, with peak monthly averages reaching almost 415 ppm.  With global emissions not really declining, the numbers just get higher and higher.

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Faster CO₂ rise expected in 2019

Photo, posted March 18, 2006, courtesy of Darin Marshall via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Your Children’s Yellowstone

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Yellowstone National Park was the first national park in the US and according to some sources, the first in the world.  It is the home of charismatic megafauna and stunning geysers that attract over four million visitors a year.  It is the only place in the United States where bison and wolves can be seen in great numbers.  And it is changing.

Over the next few decades of climate change, Yellowstone will quite likely see increased fire, less forest, expanding grasslands, shallower, warmer waterways, and more invasive plants.  All these things will alter how and how many animals move through the landscape.   Ecosystems are always changing, but climate change is transforming habitats so quickly that many plants and animals may not be able to make the transition at all.

Since 1948, the average annual temperature in the Greater Yellowstone ecosystem has gone up by 2 degrees Fahrenheit.  On balance, winter is 10 days shorter and less cold.  The Northern Rockies snowpack has fallen to its lowest level in eight centuries. Summers in the park are warmer, drier, and increasingly prone to fire.

Non-nutritious invasive plants like cheatgrass and desert madwort have replaced nutritious native plants.  When plants like these take over, they suck moisture out of the ground early so that bison and elk cannot be sustained throughout the summer.

The behavior of elk and other animals is already changing, with many staying outside the park to nibble lawns and alfalfa fields.  In turn, wolves go where the elk go.   Forests and waterways are changing as well.

The rapid changes going on at Yellowstone mean that the park that our children and grandchildren will visit in the future is likely to be a very different one from the Yellowstone we remember.

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In Yellowstone National Park, warming has brought rapid changes.

Photo, posted September 7, 2016, courtesy of Mike Yang via Flickr.  

Earth Wise is a production of WAMC Northeast Public Radio.

Hurricanes Are Slowing Down

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According to a new study recently published in the scientific journal Nature, some hurricanes are moving slower and spending more time over land, which is leading to catastrophic rainfall and flooding. The speed at which hurricanes track along their paths – known as translational speed – can play a major role in a storm’s damage and devastation.  17

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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.

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Measuring Earth’s Outgoing Energy

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The earth’s energy imbalance is the difference between the amount of solar energy absorbed by the earth and the amount of energy the planet radiates back into space as heat.  If the imbalance is positive, that is, if more energy is coming in than going out, then the earth will get warmer over time.  If the imbalance is negative, then the planet will get cooler. 

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