Guardian Images of Global Warming Part 2 – A Starved Dead Polar Bear

In the Part 2 of my look at Ashley Cooper’s photographs of global warming published in The Guardian on June 3rd I concentrate on the single image of a dead, emaciated, polar bear.
The caption reads

A male polar bear that starved to death as a consequence of climate change. Polar bears need sea ice to hunt their main prey, seals. Western fjords of Svalbard which normally freeze in winter, remained ice free all season during the winter of 2012/13, one of the worst on record for sea ice around the island archipelago. This bear headed hundreds of miles north, looking for suitable sea ice to hunt on before it finally collapsed and died.

The US National Snow and Ice Data Center (NSIDC) has monthly maps of sea ice extent. The Western Fjords were indeed ice free during the winter of 2012/13, even in March 2013 when the sea ice reaches a maximum. In March 2012 Western Fjords were also ice free, along with most of the North Coast was as well.  The maps are also available for March of 2011, 2010, 2009 and 2008. It is the earliest available year that seems to have the minimum extent. Screen shots of Svarlbard are shown below.

As the sea ice extent has been diminishing for years, maybe this had impacted on the polar bear population? This is not the case. A survey published late last year, showed that polar bear numbers has increased by 42% between 2004 and 2015 for Svarlbard and neighbouring archipelagos of Franz Josef Land and Novaya Zemlya.

Even more relevantly, studies have shown that the biggest threat to polar bear is not low sea ice levels but unusually thick spring sea ice. This affects the seal population, the main polar bear food source, at the time of year when the polar bears are rebuilding fat after the long winter.
Even if diminishing sea ice is a major cause of some starvation then it may have been a greater cause in the past. There was no satellite data prior to the late 1970s when the sea ice levels started diminishing. The best proxies are the average temperatures. Last year I looked at the two major temperature data sets for Svarlbard, both located on the West Coast where the dead polar bear was found. It would appear that there was a more dramatic rise in temperatures in Svarlbard in the period 1910-1925 than in period since the late 1970s. But in the earlier warming period polar bear numbers were likely decreasing, continuing into later cooling period. Recovery in numbers corresponds to the warming period. These changes have nothing to do with average temperatures or sea ice levels. It is because until recent decades polar bears were being hunted, a practice that has largely stopped.

The starvation of this pictured polar bear may have a more mundane cause. Polar bears are at the top of the food chain, relying on killing fast-moving seals for food. As a polar bear gets older it slows down, due to arthritis and muscles not working as well. As speed and agility are key factors in catching food, along with a bit of luck, starvation might be the most common cause of death in polar bears.

Kevin Marshall

Guardian Images of Global Warming Part 1 – Australian Droughts

On Friday June 3rd the Guardian presented some high quality images with the headline

Droughts, floods, forest fires and melting poles – climate change is impacting Earth like never before. From the Australia to Greenland, Ashley Cooper’s work spans 13 years and over 30 countries. This selection, taken from his new book, shows a changing landscape, scarred by pollution and natural disasters – but there is hope too, with the steady rise of renewable energy.

The purpose is to convince people that human-caused climate change is happening now, to bolster support for climate mitigation policies. But the real stories of what the pictures show is quite different.  I will start with three images relating to drought in Australia.

Image 5

Forest ghosts: Lake Eildon in Victoria, Australia was built in the 1950’s to provide irrigation water, but the last time it was full was in 1995. The day the shot was taken it was at 29% capacity with levels down around 75ft.

Data from Lake Eildon (which is accessible with a simple search of Lake Eildon capacity) links to a graph where up to 7 years of data can be compared.

In 1995 the dam was not at full capacity, but it was full, for a short period, in the following year. However, more recently after the recent drought broke, in 2011 the reservoir was pretty much full for all the year.

But were the low levels due to more extreme drought brought on by climate change? That is very difficult to determine, as Lake Eildon is an artificial lake, constructed to provide water for irrigation occasional hydro-electric power as well as recreational facilities. The near empty levels at the end of the biggest drought in many decades could be just due a failure to predict the duration of the drought, or simply a policy of supplying irrigation water for the maximum length of time. The fact that water levels never reached full capacity for many years is indicated by a 2003 article in The Age

The dam wall at Lake Eildon, Victoria’s biggest state-run water storage, has been declared unsafe and will need a $30 million upgrade if the lake is to be refilled.

The dam, which is at its lowest level since being completed in 1956, will be restricted to just 65 per cent capacity because it no longer meets safety standards for earthquakes and extreme floods.

Image 6

Forest destroyed by bush fires near Michelago, New South Wales, Australia.

The inference is that this is caused by global warming.

According to Munich Re

The majority of bushfires in southeast Australia are caused by human activity

Bushfire is the only natural hazard in which humans have a direct influence on the hazard situation. The majority of bushfires near populated areas are the consequence of human activity. Lightning causes the smaller portion naturally. Sometimes, a carelessly discarded cigarette or a glass shard, which can focus the sun’s rays is all it takes to start a fire. Heat from motors or engines, or electric sparks from power lines and machines can ignite dry grass. Besides this accidental causes, a significant share of wildfires are started deliberately.

Humans also change the natural fire frequency and intensity. They decrease the natural fire frequency due to deliberate fire suppression near populated areas. If there is no fuel-reduction burning in forests for the purposes of fire prevention, large quantities of combustible material can accumulate at ground level.

Surface fires in these areas can become so intense due to the large amounts of fuel that they spread to the crowns of the trees and rapidly grow into a major fire. If humans had not intervened in the natural bushfire regime, more frequent low-intensity fires would have consumed the forest undergrowth and ensured that woodland grasses and scrubs do not proliferate excessively.

David Evans expands on the issue of fuel load in a 2013 article.

Like with the water levels in an artificial lake, forest fires are strongly influenced by the management of those forests. Extinguishing forest fires before they have run their natural course results in bigger and more intense fires at a later date. More frequent or intense droughts would not change this primary cause of many horrific forest fire disasters seen in recent years.

Image 7

Where has all the water gone?: Lake Hume is the largest reservoir in Australia and was set up to provide irrigation water for farms further down the Murray Basin and drinking water for Adelaide. On the day this photograph was taken it was at 19.6% capacity. By the end of the summer of 2009 it dropped to 2.1 % capacity. Such impacts of the drought are likely to worsen as a result of climate change. The last time the water was anywhere near this road bridge was 10 years ago, rendering this no fishing sign, somewhat redundant.

Again this is old data. Like for Lake Eildon, it is easy to construct graphs.

Following the end of the drought, the reservoir came back to full capacity. Worsening drought is only apparent to those who look over a short time range.

When looking at drought in Australia, Dorothea Mackellar’s 1908 poem “My Country” provides some context. Written for a British audience, the poem begins

I love a sunburnt country,

A land of sweeping plains,

Of ragged mountain ranges,

Of droughts and flooding rains

To understand the difference that human-caused climate change is having on the climate first requires an understanding of natural climatic variation over multiple time-scales. It then requires an understanding of how other human factors are influencing the environment, both intended and unintended.

Kevin Marshall