Evidence of Global Warming*

by

J. Ernest "Sunny" Breeding, Jr., PhD Geophysics

Loss of Ice

Worldwide

The loss of ice on our planet is historically unprecedented. That includes glacial retreat in West Antarctica, the Canadian and Alaskan costal mountains, Europe, and the Himalayan Massif (Radford, August 2015). The river of ice from the Jakobshavn glacier in Greenland is moving at an accelerated rate that is of great concern. Careful studies of one hundred glaciers worldwide show that glaciers everywhere are retreating, and at an accelerated rate. The observed loss of ice is 1.6 feet (.5 meter) to 3.3 feet (1 meter) of thickness each year. This is two to three times the corresponding average ice loss in the 1900s. Clearly, the Earth is changing in disturbing ways that are not normal in human history.

Muir Glacier retreating.

Fig. 2.1. Muir Glacier in Alaska. Picture on the left was taken in August 1941 and the one on the right in August 2004. (NSIDC of NOAA) See References for the sources of figures.

There are numerous examples of Mountain ice being lost all over the world. A good example of the retreat of a glacier is seen in Fig. 2.1. The picture on the left of Muir Glacier was taken by William O. Field on 13 August 1941 and the picture of the same area was taken again by Bruce F. Molnia on 31 August 2004. The glacier is found in Glacier Bay National Park and Preserve west of Juneau, Alaska. In the 63 year period the glacier retreated by more than 7 miles (12 kilometers) and its thickness decreased by 875 yards (800 meters) according to Molnia of the United States Geological Survey (USGS).

Glacier decline.

   

Length variation of glacier tongues.

Fig. 2.2. Glacier decline. (USGCRP)

   

Fig. 2.3. Length variation of glacier tongues. (IPCC)

The total loss in glacier ice between 1960 and 2005 is shown in Fig. 2.2. The amount is huge. To comprehend the amount think of a building with a floor that is a mile (1.6 kilometers) on each side and that the height from the floor to the ceiling is also one mile. The volume of that building would be one cubic mile. During the 45 years of this study we lost about 2,250 buildings that size of glacier ice. Since 2005 we have lost more ice and at a greater yearly rate. Fig. 2.3 displays the loss in the length of glacier tongues since 1700. The important thing to note is that the result is nearly the same for the Atlantic, Alps, Southern Hemisphere, Asia, and Northwest America. This is a world wide phenomena. From the figure it is obvious that the retreat of glaciers significantly increased in the 1900s. Note that the values are zero for 1950 since the data for all years were compared to the 1950 values.

The mountain glaciers worldwide, such as those in Alaska, Canada, and Chile, account for less than one percent of the volume of the world’s ice (American Geophysical Union Staff, June 2015). Most of the planet ice is found in ice sheets on Antarctica and Greenland. Despite their low percentage of the world's ice volume, mountain glaciers are currently disappearing at such a rapid rate that their loss is responsible for one-third of the global rise in sea level.

We talk of glaciers and ice sheets. If the area of the ice is more than 12 million acres (4.86 hectares) it is an ice sheet (Kahn, March 2016), otherwise a glacier.

Loss of Arctic Sea Ice

There are many examples of global warming in all parts of the Earth. But none are more clear than those found at the higher latitudes. The polar regions are the first to show the effects of climate change.

Loss in Arctic sea ice.

Fig. 2.4. Loss in Arctic sea ice. (USGCRP)

The loss in Arctic sea ice due to melting in the summer months is quite dramatic as seen by comparing the pictures taken from satellites in 1979 and 2007, which are presented in Fig. 2.4. Each picture was taken when the area of the ice reached its minimum value after the summer melt. This occurs in September, but due to the warming of the Earth there is on average a greater loss of ice in September now than in previous years. The amount of ice lost to the summer melt is more than had been predicted. This is alarming, and shows that the climate is changing faster than expected. Once freezing temperatures return the amount of sea ice grows again until the summer months return. The greatest extent of the growing ice typically occurs in March, but has occurred in February (Thompson, March 2016). A fascinating look at some of the ongoing research in the Polar Regions is described in a video by Dr. Robin E. Bell and other scientists at the Lamont-Doherty Earth Observatory of Columbia University.

Loss in Arctic sea ice.

Fig. 2.5. Loss in Arctic sea ice in 2013. (Climate Central)

The loss in Arctic sea ice in 2013 was not as bad as in some years, but it was still quite significant. Figure 2.5 illustrates in a dramatic way how much ice is lost. The amount of sea ice that was lost is shown equal to the states from Tennessee to Maine. That is a large area. The ice is also thinner than what had been normal some years ago. The long-term trend has been to greater losses in both the extent and the thickness of the sea ice. Due to the continued warming of the Earth the Arctic sea ice is expected to eventually disappear by September or earlier, possibly by mid-Century. (Freedman, 19 September 2013) That is not good news.

During the 2014 - 2015 winter there was less ice in the Arctic than during any winter since measurements were made by satellite (Hackman, 2015). This finding reinforces the prediction that the Arctic will be completely free of ice during summers by about 2040. As the Earth warms the ice starts melting sooner and is melting faster. A consequence of this is the zooplankton now contains a lot less fat. This affects the fish that feed upon the zooplankton, the seals that feed upon the fish, and then the polar bears that feed upon the seals. The whole food chain is being disturbed by a warming Earth. Humans will also be badly affected by the many changes that will take place in the Arctic and elsewhere.

Loss of Ice in Greenland

Greenland is the world’s largest island (McKie, 2015). It is covered mostly with ice. The average thickness of the ice sheet is more than a mile, and the thickness grows to two miles in places (Mooney, December 2014). If the entire Greenland ice sheet were to melt it would raise sea level by about 23 feet (7 meters). For this to happen it would likely take a very long time, perhaps one or more centuries. Because of unknown factors, such as how much greenhouse gas emissions will be added in the future, it is impossible to predict an exact date. But the global sea level only has to rise by several feet (1 meter) to cause major damage.

In 2015 significant changes were confirmed in the melting of the Greenland ice sheet. The ice is melting at an accelerated rate due to warmer summer temperatures and because the ice has turned darker, likely due to soot blown there from wildfires in places like Siberia, Alaska, and Canada (Kahn, July 2015). As the ice turns darker it absorbs more incoming radiation from the sun leading to more meltwater. The melting of Greenland’s ice sheet is considered responsible for 30 percent of the rise in sea level since the 1990s.

From satellites it has been observed that there was a sudden loss of a lot of ice from Greenland's Jakobshavn Isbrae Glacier in the southeast part of the island (Freedman, August 2015). The loss occurred between 14 -16 August 2015. Data from satellites show that in a single or multiple calving events the glacier lost an area of 4.8 square miles (12.5 square kilometers). From what is known it is logical to assume that the ice was about 4,500 feet (1,400 meters) thick. That is enough ice to cover the entire Manhattan Island by a layer of about 1,000 feet (300 meters). Between 1850 and 2010 the glacier has retreated by 25 miles (40 kilometers), with the retreat accelerating in recent years. This glacier is of concern because it could add more to the rise in sea level than any other feature in the Northern Hemisphere. To describe what is happening another way, the river of ice from the Jakobshavn glacier in August 2015 (Radford, August 2015) is moving at the rate of 150 feet per day (46 meters per day). This is twice the speed that was recorded in 2003 and four times as fast as was measured in 1997. This glacier by itself (Mooney, August 2015) could raise sea level by 3.3 feet (1 meter) if it were to completely melt.

The surprising results of an important survey of the seafloors around 14 glaciers in West Greenland was reported by Rasmussen (April 2016). The ocean depths were found to be as much as several thousand feet (several hundred meters) deeper than previously thought. That is a significant difference and means that Greenland has a number of glaciers with their lower portions in water. These marine glaciers melt both from warm air on their tops and from the warm water on their bottoms. As a result, these glaciers will melt more rapidly than if they only melted from air at their tops as originally assumed. In the case of these glaciers the melting is further enhanced in that the warmer salty water sinks to the bottom as the lighter fresh Arctic river runoff water stays in the top ocean layer.

Most of the meltwater from Greenland's ice sheet has come from glaciers in the southeast and southwest. But as the Earth warms glaciers in the colder northeastern part of the island are contributing meltwater to the ocean as well (Thompson, November 2015). It is easy to see why sea level is rising at an accelerated rate do to Greenland alone, which is not good news.

Loss of Ice in Iceland

Iceland's glaciers are receding (Iceland Monitor Staff, March 2016). An example is the Breioamerkurjokull glacier. It has lost 1,968 feet (600 meters) of ice in one year. The ice caves are also receding by massive amounts of ice. The loss in ice will only worsen in the future due to global warming, and this is not good news for Iceland.

Loss of Ice in Alaska

Due to its higher latitude the temperature is rising faster in Alaska than in the continental United States (Coombs, June 2015). In the last sixty years the average Alaskan temperature has risen twice as fast as the continental United States. The result is Alaskan mountain glaciers are melting at an accelerated rate. Due to the warming the tidewater glaciers that end in the oceans and seas lose mass by caving chunks into the water as well as through melting. Inland there are also glaciers on land and lakes that lose mass by melting. The loss in Alaskan glaciers is significant as it amounts to one third of the World’s loss from ice sheets. To appreciate how much this contribution from Alaska is, consider that every seven years the ice loss would cover the entire state with one foot (0.3 meter) of water. Sea level is rising.

Loss of Ice in Antarctica

In the world there are large ice sheets in Greenland, described above, and Antarctica. Between them they hold 99% of the ice on our planet (Evans, June 2015). The Antarctic ice sheet, which is really divided into two ice sheets, is the size of the Continental United States and Mexico combined. The ice ranges in thickness from one mile to three miles. The Antarctic ice sheets have significant differences. The much larger, older, and more stable ice sheet is referred to as the East Antarctic ice sheet. By contrast, the younger West Antarctic ice sheet is undergoing significant changes. On land near the sea the Antarctic glaciers are unusual in that the ice extends into the sea as floating ice shelves. The thick ice shelves add stability in that they anchor somewhere and slow the flow of ice from land into the sea.

The maximum extent of the sea ice surrounding the Antarctica continent has been increasing during winter months in recent years (Thompson, October 2014). So why is the ice spreading out over a larger area around Antarctica? There appear to be two reasons that explain it. First the winds are blowing the ice smearing it out over a larger area. Then the fresh meltwater from the warming of the glaciers freezes filling in ice in the water near the continent left without ice.

Because of the massive amount of ice in Antarctica, the continent has the potential to raise sea level by catastrophic amounts (Upton, August 2014). If all of its ice were to melt sea level would rise by about 200 feet (61 meters) (Wikipedia, Antarctica). But the contribution so far of melting Antarctic ice sheets to the annual global rise in sea level is only one-eight of the total amount. Why is this so much less than the contribution from Greenland and the mountain glacers? There are major differences. The Greenland ice is melting largely due to the warming effect of the air temperature. By contrast Antarctica is further from the equator than Greenland, and the air temperature stays colder not being as effective in melting the ice from the top. But as the Earth gets warmer and warmer the contribution to sea level rise from Antarctica will grow larger and larger, and that is of great concern.

Of particular concern is the West Antarctic ice sheet which is unstable, and if all of its land ice melted sea level would rise by about 13 feet (4 meters) (Kahn, August 2015). There are a number of glaciers that ring the West Antarctic ice sheet. The three big glaciers are Pine Island, Thwaites, and Smith, and they are losing mass at a rapid rate. The glaciers extend from the main ice sheet where they become ice shelves that float in the water, restricting the movement of the land ice behind them. The glaciers are becoming more vulnerable for two reasons. Over the last fifty years the average temperature has risen by 4.3 degrees Fahrenheit (2.4 degrees Centigrade). The warmer air temperatures are causing the ice to melt from the top. The second reason is unusual. These glaciers rest on rock that is below sea level. As a result, water is getting under the land ice causing it to melt from below and the water makes the ice slippery. Compounding the situation is the slope of the rocky ocean bottom which is downward towards the continent's center. So the land ice, if unrestricted by an ice shelf, tends to slide downhill towards the sea where it collapses under its own weight. With the path clear the ice behind follows along.

There have been a number of studies looking at what it would take for the entire West Antarctic ice sheet to completely disintegrate. Grumbling (November 2015) summarizes two of the investigations. In the ice sheet the Pine Island and Thwaites Glaciers are vulnerable. Model studies show that if these two glaciers completely retreat the rest of the West Antarctic ice sheet cannot survive. It is only a question of how long it takes for this to happen. A floating ice shelf melts from both its top and bottom. Once the ice shelves are gone the land ice collapses into the ocean, as described above, causing sea level to rise. Incoming sea water works on the remaining ice sheet by creating melt channels leading eventually to its complete destruction. It is thought that this process, which could take centuries, has already begun and that it maybe unstoppable. There is speculation that a tipping has been reached. Note that sea level would only have to rise by several feet (1 meter), not all of the 13 feet (4 meters), to cause major damage to our coastal cities and properties.

Gillis (March 2016) and Jones (May 2016) describe a more extensive investigation of the disintegration of the West Antarctic ice sheet by David Pollard and Robert M. DeConto. To make predictions of the disintegration of the ice sheet as a function of time they developed an improved computer model. It includes data describing the land, ice, and water environment. They took into account the breakup of the floating ice shelves that hold back the land ice. The land ice is in the form of sheer cliffs that stretch high above their rocky base, which is below sea level. The model takes into account the continuing collapse of the sheer ice cliffs due to their own weight as they move down hill on the sloping ocean bottom. In time, perhaps centuries, with high greenhouse emissions the West Antarctic ice sheet can be completely destroyed. The model was tested with success using data from 125,000 years ago when sea level was 20 to 30 feet (6 to 9 meters) higher than it is today.

Pollard and DeConto found that if they assumed a continued high emission of greenhouse gases into the atmosphere that the partial destruction of the West Antarctic ice sheet could raise sea level by 3 feet by the year 2100. Adding to that the meltwater from other parts of the Earth sea level would rise by 5 to 6 feet (1.5 to 1.8 meters). This is about double the amount that has previously been assumed. It was found if the continued high rate of greenhouse gase emissions contiunes sea level rises at a more rapid rate reaching about 1 foot per decade by the middle of the 22th century, which is downright freightening. But they did find that if greenhouse gas emissions are sufficiently reduced the West Antarctic ice sheet would not be completely destroyed, as other investigators have concluded, but is stoppable. We can only hope they are right!

It is also important to consider the East Antarctic ice sheet. Most of its ice sits on a rocky bottom above sea level (Jones, May 2016). But the Totten Glacier has been found to be melting and thinning faster than anywhere else in East Antarctica (Evans, June 2015). It is also thought that warmer water is getting under the glacier causing it to melt from below. If all of the ice associated with the Totten Glacier were to melt it would add 11 feet (3.4 meters) to the global sea level. As the Earth continues to warm we can expect that other parts of the East Antarctic ice sheet will yield meltwater adding to the rise in sea level.

It is clear from these investigations that greenhouse gas emissions must be reduced sufficiently, and soon. Otherwise, in the long term many cities like New York City, New Orleans, Miami, and numerous coastal cities will be devastated by flooding from the continuing rise in sea level. It is not a question of what will happen but when. As we collect more data and analyze the results we will better define the problem and the time scale of events. To prevent catastrophic flooding on Earth we must stem the flow of meltwater from Antarctica by reducing the emissions of greenhouse gases. At the same time this will reduce the rise in sea level from Greenland and the mountain ice in other parts of the Earth.

Sea Level Rise

Rise in sea level.

Fig. 2.6. Rise in sea level. (IPCC)

With the meltwater of glaciers and ice sheets draining into the oceans the mean sea level has risen. In Fig. 2.6, which shows data from several different investigators, it is seen that the mean sea level has risen by about 8 inches (200 millimeters) since 1870. Considering that about 70% of the globe is covered by the oceans and seas, that is a lot of meltwater. A disturbing fact is that sea level is now rising at the rate of 1.2 inches per decade (3 centimeters per decade). That is about 1/8 of an inch (0.3 centimeters) per year. This is twice the rate during the twentieth century (Hansen, 2009.) If our planet ice continues to melt at an ever increasing rate or breaks up into more and more icebergs, which is likely, the future of many coastal cities and other coastal developments are in doubt.

Other Results of Global Warming

Polar Regions and High Latitudes

Permafrost

Thawing permafrost.

Fig. 2.7. Thawing permafrost damaged railroad track. (livescience.com)

 

Although the loss of the planet ice and the resulting rise in sea level are some of the main problems due to global warming, there are other significant problems. The picture of the railroad tracks in Fig. 2.7 was taken in the northern Tibetan Plateau. The tracks became useless because of thawing permafrost; what was once a solid footing is not anymore. In Alaska and other high latitude regions there are homes and other buildings that are now collapsing because they were built on permafrost, which is now thawing. The ground had been solid for many thousands of years, so no one expected the permafrost to thaw.

Permafrost is subsurface soil that remains frozen throughout the year. It is found in the Arctic region, but aldo extends south of the Arctic Circle at latitude 66 degrees 33 minutes. The southern boundary of permafrost is moving north as the Earth warms due to global warming. In the Northern Hemisphere about 25 percent of the land is permafrost (Thompson, December 2015). Much of it is now vulnerable to melting durning the summer months.

Canada has the world's longest coastline (Zerehi, April 2016) at more than 125 thousand miles (200 thousand kilometers). More than 70 percent of the coastline is located in Northern Canada, and it is eroding because the frozen ice that once protected it from storm waves for thousands of years is now melting. This is a serious problem for many coasts in the Arctic or near Arctic regions.

Wildlife

Creatures and plants of the Earth are severely affected by climate change because they require a narrow range of environmental conditions to survive. For example, there are 20,000 to 25,000 polar bears in the world (Zuckerman, July 2015). Many of them are on the Arctic sea ice in Alaska. When standing they can be 11 feet (3.35 meters) high and can weigh 1,400 pounds (635 kilograms). Their preferred habitat is the sea ice. They spend considerable time on the ice and use it to get to seals, their main source of food. The loss of sea ice during summer months is having a devastating impact on them. During this time many polar bears are now going hungry, and it is especially a problem for mother polar bears. Since a much greater loss of summer sea ice is expected in coming decades due to global warming the population of polar bears will very likely decrease significantly. Some species of seals are also in danger.

Walruses like to hang out and rest on the sea ice in the Arctic Ocean on the North Slope of Alaska (Harvey, August 2015). This puts them close to their food source of shellfish on the ocean bottom. In some recent years during the summer months the ice has melted so much that tens of thousands of walruses have no choice but to move to the shore in places like Barrow, Alaska. This makes it harder for them to get to food and also makes them vulnerable to polar bears. A polar bear can cause a stampede to the water of thousands of walruses with numerous small adults and calves being injured or trampled to death. The melting of sea ice will only worsen as the Earth becomes warmer.

Penguins.

Fig. 2.8. Penguins. (USGCRP)

Penguins are pictured in Fig. 2.8. The Adelie Penguins near the Antarctic Peninsula are suffering because of the rapid increase in warming and the subsequent loss of sea ice. Because of the loss of sea ice the Krill they eat is less available to them. Due to the longer and longer summers the ice-free time has lengthened, which is not good for polar bears, penguins, and some other living beings. The loss of sea ice also means less protection of the coasts from storm waves, leading to erosion of land.

Examples in Temperate and Tropical regions

Drought & famine.

Fig. 2.9. Drought and famine. (USGCRP)

Temperate and tropical regions also show evidence of global warming. Fig 2.9 is a picture where there is drought and famine. One of the most discussed places for this is the Sahel desert in Africa, south of the Sahara Desert. The Southwest in the United States is also experiencing drought. In both cases global warming is thought to be a factor. It is also necessary to take into account the Southern Oscillation (El Nino and La Nina), which has had a major impact on weather in many parts of the world for many years.

Cities are usually hotter than rural areas, but global warming has made them worse (Climate Central Staff, 2014). More than 80 percent of Americans live in cities, which have become urban heat islands, leading to serious health effects. City heat during the summers has become the number 1 weather-related killer in the United States. In particular, days over 90 degrees Fahrenheit (32 degrees Centigrade) are associated with ozone pollution that can cause asthma attacks, heart attacks, and other health related issues. The effects of urban heat islands can be reduced by adding more trees, parks, and buildings with white roofs.

Phoenix is hotter.

Fig. 2.10. Phoenix is hotter. (USGCRP)

In Phoenix the average number of hours per summer day that the temperature exceeds 100 degrees Fahrenheit (37.7 degrees Centigrade) has doubled in the past 50 years. The upward trend is seen in Fig. 2.10 (red line). In addition to the United States, heat related deaths are occurring in Europe, Australia, and other parts of the planet. As the Earth continues to warm the number of hot days will increase.

Dead trees.

Fig. 2.11. Dead trees. (USGCRP)

Fig. 2.11 is an example of dead trees. Increasingly many trees are being killed by bark beetles. For example, in the Northern Rocky Mountains at elevations above 9,000 feet the whitebark pine forest is dying (Fischer, 2014). The forest has been part of an ecosystem where creatures like bears and jays eat the pine seeds as part of their diet. Prior to the late 1990s the winter temperatures in the higher elevations were cold enough to kill off the pine beetles. But since 2009 the white bark pine forest has either been dead or dying because the mountain pine beetles are surviving the warmer winters due to climate change, and are killing off the trees. More than 95% of the big trees have become victims of the pine beetles. The area affected is the size of South Carolina. The same thing is happening to the white spruce forests in parts of Alaska.

Global warming would be worse if it were not for trees since the Earth’s forest absorb about one-fourth of the carbon dioxide caused by humans burning fossil fuels (Anderegg, 2015). Trees store the carbon in their stems, and they can keep it there for centuries. But in addition to insect outbreaks, because of global warming there are more frequent and extreme droughts and large wildfires. All of these slow the growth of trees or kill them releasing carbon dioxide back into the atmosphere. In regions where there are extreme droughts the trees are not as effective in absorbing carbon dioxide, and if the drought subsides it takes several years for the trees to recover to a healthy state. This problem will worsen as the Earth continues to warm.

Loss in Arctic sea ice.

Fig. 2.12. Growing season is increasing. (USGCRP)

The mild winters are also affecting the harvesting of maple syrup in New England. The problem is fewer nights with below freezing temperatures. The proper environment for harvesting maple syrup is moving north into Canada. With shorter winters the growing season for many crops has been increasing in length. In Fig. 2.12 it is seen that the growing season in the United States and Eurasia increased by 12 days from 1982 to 1999. This can be good for some and bad for others. Vineyards are now possible where they were not before. A more obvious change is the start of the fall foliage season, which is starting about two weeks later in the continental United States than it did in 1982 (Kahn, 2013). These are all examples of climate change.

Butterfly.

   

Coral.

Fig. 2.13. Butterfly. (USGCRP)

   

Fig. 2.14. Coral. (USGCRP)

Butterflies, birds, amphibians, and reptiles are other examples of living beings that must adjust to a changing climate. A butterfly is pictured in Fig. 2.13. In Europe the Apollo butterfly has been slowly moving to higher elevations in the mountains to find the temperature range it needs. In the Monteverde Cloud Forest of Costa Rica, one of my favorite places, the orange-billed nightingale thrush has moved to higher elevations as the temperature has warmed. Some animals and plants are moving to higher latitudes to find the environmental conditions that they need and have been accustomed to. The rate of movement has increased in recent years as the Earth has been warming at a faster rate (Hansen, 2009.) Once these critters and plants are no longer able to find the environmental conditions they need they will have to adapt to a warmer world or they will join the many species that are now extinct.

The oceans also have clear evidence of global warming. Coral reefs, seen in Fig. 2.14, are very fragile ecosystems. They can be damaged and even killed by very warm temperatures. In the process they change color to light yellow or white, which is called coral bleaching.

There are many more examples of climate change from all around our planet to numerous to mention here (Burroughs, 2007; Henson, 2008; Hansen, 2009, 2011; and Schmidt and Wolfe, 2009.) But it should be clear from what is presented above that the Earth is warming, and the consequences are not good.

We need data that defines climates of the past to compare with the present to determine similarities and differences. This is accomplished by a rather impressive set of measurements. We look at that next.

Pages

Page 1: Climate Change and Definition
Page 2: Evidence of Global Warming
Page 3: Measurements
Page 4: Ice Ages
Page 5: Causes of Climate Change
Page 6: Predicting the Future
Page 7: How Can We Fix Our Climate?
Page 8: References

*A slide show version of these pages on climate change is available for presentations to groups. See References for more details.

 

 

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