Tag Archives: temperature

Summer’s On The Way: How’s Earth’s Temperature?

8 Apr

With Summer on the way – Yippy – and an unseasonally hot spell 

for March/April so far in the UK, I thought I’d post a blog on Temperature,

taken from Chapter T of THE A-Z OF GLOBAL WARMING.

Temperature is generally measured using the Celsius scale,

except in the USA, where the Fahrenheit scale is used. Zero degrees

Centigrade corresponds to the temperature at which water freezes,

and 100 degrees when it boils. These temperatures are represented

as 32 and 212°F respectively.

The Earth’s average temperature, assisted by its naturally

occurring greenhouse-gas blanket, is about 15°C (59°F). The

average temperature of the human body is about 37°C (98°F), and

if temperatures get too high harmful reactions and even death

may result.

Just like a human being, if Earth’s temperature increases too

much, the planet will start to get sick and serious consequences

will result, some of which are already becoming evident.

 

 

How much has the Earth’s temperature increased?

 

The Earth’s global mean surface temperature according the Fourth

Assessment Report of the IPCC puts the rise at 0.74°C (1.33°F)

over the period 1906 to 2006.

Global temperature is measured by taking the average near-surface

temperatures over air, sea and land.

This rise may not seem like much, but according to NASA,

this means that the Earth is now reaching and passing through

the warmest period in the current interglacial period, which has

lasted for nearly 12,000 years.

 

 

How fast is Earth’s temperature rising?

 

The Earth’s temperature has risen by about 0.2°C (0.36°F) each

decade over the last thirty years. The studies show that warming

is greatest at higher latitudes of the northern hemisphere, and

larger over land compared to the oceans, as the oceans have a

much higher heat capacity compared to the land.  Air temperatures

in the Arctic region for example have, on average, actually

increased by about 5°C (9°F) over the last 100 years.

 

 

What about historical warming?

 

We know from Chapter H that the Earth has had many periods

of warming and cooling, and historically these temperature

changes have had little to do with manmade greenhouse gases,

as mankind has been emitting greenhouse gases significantly only

since the Industrial Revolution, in and about the late nineteenth

century.

Two of the most recent temperature changes took place during

the Little Ice Age, in the years 1350–1850, or thereabouts, when

temperatures dipped, and the Medieval Warm Period between

years 1000–1300, or thereabouts, when temperatures got

comparatively warmer again. An explanation for the Little Ice

Age, or Maunder Minimum is the lack of sunspot activity and

solar irradiance that occurred during this time .

 

 

What about more recently?

 

Well, temperatures have been measured accurately with scientific

instruments for about only 150 years or so. Prior to this a range

of proxy data is used, such as tree rings, ice cores, lake and sea

sediments, corals and historical records.

Researchers from NASA, Dr James Hanson and his colleague

Mark Imhoff, analysed records from 7,500 global weather stations

and used satellite observations of night-time weather stations to

identify minimal human influence, such as urban heat island effects.

The team concluded that from 1900 to 1940 it was possible the

Earth warmed partly as a result of increased levels of greenhouse

gases and partly due to natural climate variability.

Between 1940 and 1965 the Earth cooled by about 0.1°C (0.18°F),

which some scientists attribute to the increased use of aerosols

and other airborne pollutants from the burning of fossil fuels.

This was especially so in the northern hemisphere, where cooling

occurred most during this period, which can lead to increased

cloud cover, which in turn blocks and reflects incoming solar

radiation. This is a phenomenon that has been termed ‘global

dimming’. Aerosols, certainly in the northern hemisphere, have

been slowly phased out however, which may have helped reveal

the true extent of greenhouse-gas-induced warming.

The period from 1965 to 2000 showed large and widespread

warming around the world.

 

Indeed the IPCC concluded in 2001 that there is new and stronger

evidence that most of the warming observed at least over the past fifty

years is attributable to human activities.

 

 

Link between global warming and human activities?

 

There has been much debate between scientists over attribution

of climate change and global warming, and much of this discussion

has focused on a temperature graph produced in 1999 for the IPCC,

by climatologist Michael Mann and his colleagues, which showed

temperatures extending back 1,000 years. The debate became

known as the ‘hockey stick’ debate.

This name came from the graph itself, as it shows temperatures

for about 1,000 years remaining more or less constant, then from

about 1800 a sharp upward trend occurs that resembles the end

of a hockey stick.6 The reconstructions showed the 1990s to be

the warmest decade, with 1998 the warmest year ever.

The graph seems to support the warming influence human

beings have had on climate over the last 150 years or so, as

evidenced by the sudden upward trend in temperatures recorded.

Certain criticism was made of the fact that accurate temperature

records go back only 150 years, and that the data and methods

used to recreate the temperature prior to about 1850 cannot be

reliable as it comes from proxy sources such as tree rings, corals

and ice cores, etc.

It would appear however that much of the debate as to who

is responsible for global warming is now settled. While solar

intensity and even volcanoes and other natural factors can explain

variations in global temperatures in the early nineteenth century,

rising greenhouse gas levels can provide the only plausible

explanation for the warming trend over the past fifty years.7

In response to the controversy over the Mann temperature

graph, in 2006 the US Congress requested the National Research

Council prepare a report. They concluded that there was a high

level of confidence that the global mean surface temperature

during the past few decades is higher now than at any time over

the preceding 400 years. There is less confidence prior to the year

1600 to support temperature reconstructions, as there is less data

available from whatever source. There was even less confidence

about the conclusions reached that the 1990s were the warmest

decade and 1998 the warmest year. The committee did indicate,

however, that none of the reconstructions showed that

temperatures were warmer during medieval times than during

the last few decades.

The main conclusion, however, is that the build-up of

greenhouse gases in the atmosphere will cause several degrees

of warming, and this is based on the laws of physics and chemistry.

The link between greenhouse gases and temperature is well

established, as we know from Chapter G, so when additional

CO2 is added to the atmosphere, by burning fossil fuels, the

temperature is going to increase. This has been confirmed by

reliable scientific instruments over the last 150 years.

 

 

How high will temperatures go?

 

For the last three decades temperatures have been rising by about

0.2°C (0.36°F) per decade. There is evidence however that the

warming may accelerate as positive feedback mechanisms come

into play. Examples would be the release of methane from the

ground as the permafrost starts to melt, thus accelerating the

warming. Studies already indicate that warming is greater over

the northern hemisphere. As the snow and ice melt in the Arctic

regions, darker surfaces are uncovered, which reduces the albedo

effect of the ice/snow-covered areas, which allows more sunlight

to be absorbed, thus increasing warming. Likewise as the

atmosphere warms it is able to hold more water vapour (itself a

greenhouse gas), which allows it to trap more heat. These are two

examples of positive feedback mechanisms.

It is not yet possible however to determine what temperature

will result from a certain level of greenhouse gas.

It is estimated that if greenhouse gas could be stabilised at

today’s level of about 430 ppm CO2 equivalent, the Earth would

be committed to an eventual temperature increase of about 1–

3°C (1.8–5.4°F) above pre-industrial levels.

 

 

Projected CO2/temperature level scenarios

 

The amount the Earth’s temperature goes up depends on

greenhouse gas levels in the atmosphere.

Projections of future warming depend on projections of global

emissions. If emissions were to remain at today’s levels, then

greenhouse gas would reach about 550 ppm CO2e by about 2050,

based on the current annual increase of 2.5 ppmv CO2e. This would

commit the world to a temperature rise of about 2–5°C (3.6–9°F).

The IPCC however projects that without intervention

greenhouse gas levels will rise to 550–700 ppm CO2e by 2050,

and 650–1,200 ppm CO2e by 2100! This would cause temperature

rises of between 1.5–4.4°C (2.7–7.9°F) and 1.8–5.5°C (3.2–9.9°F)

respectively, just on the lower forecasts of 550 and 650 ppm CO2e

levels alone!

‘A temperature rise of 2–3°C (3.6–5.4°F) above present

levels would put the Earth at a temperature not

experienced for three million years and far outside the

experience of human civilisation.’

The Earth is already committed to a 1–3°C rise (1.8–5.4°F) on

current greenhouse gas levels. If the Earth warms by a further

1°C (1.8°F), NASA scientists point out that this will be the warmest

Earth has been for the past 1,000,000 years. At 2 or 3°C higher

(3.6–5.5°F), the Earth would become a different world from that

we know. As mentioned above, the last time this occurred was

about 3,000,000 years ago, and sea levels are estimated to have

been twenty-five metres higher (eighty feet) than present!

There seems to be no alternative therefore other than

humankind reduce greenhouse gas emissions, significantly, and

fast, in order to prevent disastrous consequences. The big

problem is that like a huge oil tanker trying to make a U-turn,

even if emissions could be halted now, the effects of current

levels will continue to cause temperatures to rise for a long time

to come.

 

 

Any evidence of increasing temperatures currently

affecting Earth?

 

According to the WWF, evidence comes from the bleaching and

degradation of coral reefs (discussed further in Chapter V), due

to increasing sea temperatures, which could degrade Australia’s

Great Barrier Reef in a single human lifetime. Alpine forests

struggle to spread to higher, cooler locations, and glaciers are

melting all over the world.

The Caribbean saw its warmest ever ocean temperature in 2005.

Scotland in the UK saw its hottest year on record in 2003, which

caused hundreds of adult salmon to die, as the water became too

warm for the fish to extract oxygen from it.

New modelling work by the UK’s Hadley Centre shows that

the summer of 2003 was Europe’s hottest for 500 years.

In the Arctic, sea ice measurements in 2007 recorded the smallest

sea-ice cover ever at the end of the summer melt season.

In 2003, the world’s major cities sweltered under heatwaves.

In France, during the summer of 2003, the heatwave killed about

14,800 people in Paris alone, according to official figures released

in September 2003.

Summer temperatures have been analysed in sixteen of Europe’s

cities, which show that the continents’ capitals have warmed by

up to 2°C (3.6°F) in the last thirty years.

London is the city where average maximum summer

temperatures increased the most, up 2°C (3.6°F) over the last

thirty years, followed by Athens and Lisbon (1.9°C or 3.4°F),

Warsaw (1.3°C or 2.3°F) and Berlin (1.2°C or 2.1°F).16

Between 2000 and 2005, average summer temperatures in

thirteen out of sixteen cities looked at were at least 1°C (1.8°F)

higher than during the period 1970–1975.

 

 

Earth’s warmest years

 

According to climatologists at NASA’s Goddard Institute for Space

Studies the five warmest years since the 1880s have been;

 

1 2005/2010

2 1998

3 2002

4 2003

5 2006

 

The year 2005 and 2010 therefore have been the hottest so far, though they

share this accolade with 1998, which was virtually as hot. Year

1998 temperatures were enhanced however by the strongest

tropical El Niño for almost a century, which boosted temperatures

above the level they otherwise would have been. As the El Niño

gets underway in the topical Pacific Ocean, 2007 could be even

hotter, bringing with it increased warmth. 

 

 

A 2°C (3.6°F) increase limit

 

The WWF is advocating that temperatures cannot be allowed to

rise by more than 2°C (3.6°F) above pre-industrial levels, otherwise

dangerous climate change may occur. The Earth has already

warmed by 0.74°C (1.33°F), which means another 1.3°C rise (2.34°F)

could be too much.

The 2°C (3.6°F) threshold is based on the best available science

and is accepted by many governments including the prime

ministers and presidents of all twenty-five EU member states.

The only way to prevent temperatures staying below this level

is for CO2 concentrations to stay below about 400 ppmv, the

equivalent to greenhouse gas levels of around 450co2e. If this were

possible, staying below 2°C (3.6°F) is likely, according to climate

models.  Levels of CO2 however are already at 395 ppmv, which

means the chance of stabilisation below 400 ppmv is therefore

very unlikely.

 

 

What would a 2°C (3.6°F) rise in temperature

mean?

 

The WWF has looked at three regions to see what a 2°C (3.6°F)

temperature rise would mean for those regions.

 

 

The Mediterranean

 

Everyone enjoys going on holiday to the ‘Med’, with its beautiful

warm climate. However, as temperatures rise in the region, water

shortages could become common as annual rainfall could decrease

by twenty per cent, and more heat-waves cause all-year-round risk

from serious forest fires, as maximum temperatures could rise

by up to 5°C (9°F).

 

 

The Arctic

 

Temperatures would rise by about 3.2°C (5.7°F) here, maybe even

double that if temperatures rose by 2°C (3.6°F) elsewhere. Less

ice means more heat absorption as the darker water absorbs the

sun’s energy. Arctic summer ice could totally disappear, leaving

wildlife habitats, such as the polar bears, deteriorating or

destroyed.

 

 

Eastern Canada

 

Important species of trees, including the sugar maple, Canada’s

national symbol, will be forced to move northwards, which could

cause problems if the trees cannot adapt. Canadian fisheries will

also struggle, which could be the final straw for the already

endangered Atlantic salmon.

These are just examples of three regions and the effects of a

2°C (3.6°F) rise in temperature. Of course, many other regions

would also suffer similar consequences.

 

According to the Stern Review on the Economics of Climate Change,

some climate models suggest that a global 2°C (3.6°F) rise above preindustrial

levels would mean that there is potential for the Greenland

ice sheet to begin melting irreversibly, a rising risk of the collapse of

the West Antarctic ice sheet, and a rising risk of the collapse of the

ocean thermohaline circulation.

 

If temperatures rose more than 5°C (9°F), which is possible if

emissions continue to grow, and positive feedback mechanisms

kick in, such as the release of CO2 from carbon sinks and methane

from permafrost, then the rise in temperatures would be equivalent

to the amount of warming that took place between the end of

the last Ice Age and today.

Such a rise in temperature would be far outside human

experience. A very sobering thought!

The Earth, like a sick human being, is already beginning to

show the effects of higher temperatures. A 2°C (3.6°F) global

temperature rise appears to be the limit recognised as causing

catastrophic climate change.

Staying below 2°C (3.6°F) requires CO2 levels to be stabilised

at 400 ppmv, and this appears unlikely as CO2 levels are already

at 395 ppmv and increasing annually. Greenhouse gas levels are

already at 430 ppm CO2e, ( 2008 level ) and rising at 2.5 ppm CO2e annually.

If this continues, the Earth may well be 2–5°C (3.6–9°F) warmer

by 2050, when greenhouse gas levels would reach about 550 ppm

CO2e.

It seems the only answer will be for all nations and all

individuals to do their bit as far as possible to prevent, or at least

reduce, greenhouse gas emissions. The science appears clear. While

it may not be possible to prevent a 2°C (3.6°F) temperature rise,

it seems everything must be done to prevent rises over and above

this level, and the window of opportunity to do so is rapidly

disappearing.

 

Key points

 

➢ Earth’s global mean surface temperature has

increased by 0.74°C (1.33°F) over a hundred-year

period, 1906–2006.

➢ Temperatures in the Arctic however have increased

by about 5°C (9°F) over a similar period.

➢ If greenhouse gases could be halted at present

levels, the Earth would still warm by about 1–3°C

(1.8–5.4°F) above pre-industrial levels (possibly

2.26°C more than present).

➢ The last time Earth was 2–3°C (3.6–5.5°F) higher

than present was 3,000,000 years ago, when sea

levels may have been twenty-five metres (eighty

feet) higher than present.

➢ The warmest year since 1880 was 2005 and 2010, virtually

on a par with 1998, when temperatures were

boosted by an exceptional El Niño year, while 2007

has become Earth’s second warmest year jointly

with 1998.

Image    

No More Ice!

12 Sep

News is just out that Arctic ice levels may now be at their lowest ever level, following the 2011 summer melt season, beating the 2007 record. NSIDC will be confirming this sometime in October 2011. 

So, with this in mind, let’s take a look at how global warming is affecting the Earth’s coldest regions and ice sheets, collectively called the cryosphere, derived from a Greek word meaning frost or cold. It is used to describe the areas of the Earth’s surface where water is in a solid form, usually snow or ice. These areas include sea ice, freshwater ice, glaciers, permafrost and snow. 

The Earth’s polar icecaps, found at the North and South poles, contain the largest concentrations of ice on Earth. The North pole is home to the Arctic, and the South pole the Antarctic. Also in the north is the massive Greenland ice sheet. Both the Antarctic and Greenland ice sheets sit on top of continents or landmasses, whereas the Arctic is a frozen ocean. Sea ice however is found in both the North and South polar regions, and in total it covers an area about twenty times the size of Canada.

WHAT IS SEA ICE ?

Well, it is simply frozen ocean water. It forms and melts in the ocean. Icebergs, glaciers, ice sheets/shelves, however, all originate on land, and are formed with fresh not saltwater. Sea ice grows in the winter months and melts during the summer. Some ice remains all year round, and about fifteen per cent of the world’s oceans are covered during part of the year.

 WHY IS IT SO IMPORTANT ?

 

Ice has a bright reflective surface, so as sunlight strikes it most of it is reflected back into space. As such, areas covered by ice don’t absorb much of the sun’s energy, allowing temperatures in the polar regions to remain cool. If higher temperatures melt the ice over time, as is beginning to happen, then more of the sun’s energy can be absorbed by the ice-free sea or land, allowing temperatures to rise further.

The term ‘albedo’ is used to determine how well a surface reflects solar energy. A surface with an albedo of zero means that it is a perfect absorber of the sun’s energy, such as a black surface. An albedo of one means that the surface is a perfect reflector, such as a white surface. Sea ice will reflect about fifty to seventy per cent of the sun’s energy. Open sea reflects about six per cent, whereas snow-covered ice about ninety per cent, simply because it’s white and therefore has a higher reflective surface.

Just as the Amazon regulates climate by absorbing and storing huge amounts of CO2, the ice-covered regions of Earth act much in the same way, by regulating temperature and reflecting large amounts of solar energy back into space. If these regions melt, then not only will ocean levels rise but temperatures will also increase.

HOW IS THE ARCTIC RESPONDING TO GLOBAL WARMING ?

 

The North pole sits right in the middle of the Arctic Ocean, which is fenced in by eight different countries. During the winter the ice extends over the entire ocean and onto the fringes of the land. During the summer, the ice retreats back into the ocean. Air temperatures in the region have, on average, increased by about 5°C (9°F) over the last 100 years, which is higher than anywhere else on the planet. This has caused Arctic sea ice to decrease by about fourteen per cent since the 1970s.

The local Inuit population have started to notice the warmer summers, the earlier break-up of the ice in spring, and extensive areas of melting permafrost in places like Alaska and Siberia. This in turn is affecting their hunting season, foundations of properties and other infrastructure in the region. Arctic sea ice has been measured by the National Snow and Ice Data Centre (NSIDC) and NASA, using satellite data, and the findings are that massive reductions in sea ice are occurring at the end of the northern summer.

The sea ice extends to about 15,000,000 square kilometres (5,792,000 square miles) during winter, and down to an average 7,000,000 square kilometres (2,703,000 square miles) during the summer. It therefore loses just over fifty per cent of ice cover after the summer melt season. The annual average extent of Arctic sea ice has decreased by about three per cent per decade since about 1980, which is the equivalent of an area of about 750,000 square kilometres (289,575 square miles). The amount of ice left after the summer melt is also decreasing by about 7.7 per cent each decade.

NSIDC measures Arctic sea-ice extent, or the area of ocean that is covered by at least fifteen per cent ice, which typically reaches its minimum in September, at the end of the summer melt season. 

In 2007, NSIDC data reveals that Arctic sea ice during the 2007 melt season plummeted to the lowest levels since satellite measurements began in 1979. The September sea-ice minimum went down to 4,130,000 square kilometres (1,594,000 square miles), the lowest September on record, shattering the previous record for the month, set in 2005, by twenty-three per cent. Computer models however have predicted the Arctic will be ice-free in the summer months from 2080 if the overall warming trend continues.

In March 2007, a fire onboard the British nuclear submarine HMS Tireless forced it to the surface. Two sailors died in the explosion. The Navy had been conducting tests under the Arctic and the data retrieved indicated that the summer Arctic sea ice may actually be gone by as soon as 2020. This however appears to be a worst-case scenario.

Arctic sea ice is about 2 to 3 metres (6.5 to 9.8 feet) thick on average, so a loss of 7,000,000 square kilometres (2,703,000 square miles) times 2.5 metres (8.2 feet) (thickness) is a considerable amount of water. Melting sea ice however does not necessarily add much to sea-level rise when it melts, much like melting ice cubes in a glass do not cause the glass to overflow. Melting glaciers and ice-covered continents however are a different matter and when they melt, sea levels will rise.

A new NASA-led study found a twenty-three per cent loss in the extent of the Arctic’s thick year-round sea ice cover during the past two winters. The scientists discovered less perennial sea ice in March 2007 than ever before. This drastic reduction is the primary cause of this summer’s fastest-ever sea-ice retreat on record and subsequent smallest-ever extent of total Arctic coverage.

Record summer melting has also meant that the usually frozen Northwest Passage waterway, which connects the Atlantic to the Pacific, has become fully navigable, a fact that may raise tensions between Canada, which maintains that the waterway lies in its territorial waters, and other countries in the region. The race is now on to exploit the Arctic’s natural resources as oil companies drill for oil there. A disaster along the lines of the Deepwater-Horizon spill, would be cataclysmic.

For a recent news article showing stark photographic differences over time between Himalayan glaciers, click here.

For more information, check out THE A-Z OF GLOBAL WARMING, the above article is taken from chapter N – No More Ice!

Alternatively for a fast paced eco-thriller, involving a race to prevent the Arctic from melting, try TIPPING POINT.

         

Global Warming – A brief Introduction.

9 Sep

The term Global Warming has been in common usage for some time now and refers to recent warming of Earth’s atmosphere,which also implies a manmade or human influence.

Earth’s atmosphere comprises many gases: oxygen, nitrogen, carbon dioxide (hereafter abbreviated to CO2) and water vapour, to name a few. These gases are collectively called greenhouse gases and they keep the Earth’s temperature at a comfortable 15°C. Without them Earth would be a chilly -18°C.

Since pre-industrial times, usually taken to be before 1750, we know from ice-core records that CO2 levels were about 280 ppm,that’s 280 parts of CO2 per million parts of air. As industrialisation got underway humankind started to farm the land more intensely than ever before, which included deforestation for agriculture and settlements. Later – since about 1850 or so – the burning of fossil fuels for energy and transport has added considerably to greenhouse gas levels, particularly CO2.

This has resulted in CO2 levels increasing to about 390 ppm, a rise of about thirty-nine per cent from pre-industrial levels – mainly as a result of burning fossil fuels.

How do we know this?

Well, data from ice-core records that go back at least 650,000 years now show us that CO2 levels have fluctuated naturally during this time between 280 and 300 ppm. CO2 levels have also been measured accurately from the top of Mauna Loa Volcano in Hawaii since 1958, and results show an increase in CO2 levels from 315 ppm to 390 ppm since that time.

Therefore CO2 is now at ninety ppm more than it has been for at least 650,000 years of Earth’s history, and increasing. It is a known scientific fact that higher levels of greenhouse gases will lead to higher temperatures, which appears to be happening now. The world has warmed by an average of 0.74 degrees during the last 100 years or so. As a result of this warming, polar ice has started to decrease and melt, and so have Earth’s land-based glaciers. This in turn is causing sea levels to rise, which is putting low-lying islands at risk of flooding or total submersion, and will eventually threaten more and more of the world’s coastal cities and regions.

Things may get worse, however, because once Earth’s atmosphere starts to warm, the warming itself may cause further positive feedback mechanisms to kick in. A warmer atmosphere holds more water vapour, which is itself a powerful greenhouse gas. This will in turn cause further warming, and so on.

Melting ice results in more sunlight being absorbed by the surrounding ‘darker’ water and land, and that results in further warming, and more melting ice. Methane deposits currently held in a frozen but stable state under the sea and under the permafrost may be released as the oceans warm and permafrost melts, which will cause further warming. This is very worrying as methane is a potent greenhouse gas and around twenty times more powerful than CO2 when talking about it’s ability to warm the Earth’s atmosphere.

This is global warming in a nut shell, however there are of course far more complex issues involved as global warming will not affect the whole planet in the same way at the same time. Some parts will experience more drought, some parts more rainfall, and some parts more extreme weather such as floods and heatwaves.

One thing is for sure,as the world warms, we will all know about it…

For more information on the subject check out THE A-Z OF GLOBAL WARMING. Or visit my website SIROSSERTHRILLERS.