Page 76 - The World About Us

Sun spots
1.1.1
1.1.1
2.2.32.3.2

What are the causes of climate change?

As we can see from the graphs on is important to understand what are energy received from the Sun, as well
page 73, there is no such thing as a the natural drivers of climate change, as changes in the Earth's orbit around
'normal' global temperature when as well as those linked to human the Sun.
measured over thousands of years, let ac vity. Human causes are mostly
alone geological mescales. There is Natural processes which influence a ributed to the burning of fossil fuels,
debate amongst poli cians, the climate include the short term impact industrial atmospheric pollu on,
scien fic community and the public, as of volcanic erup ons and the long- deforesta on, waste disposal and
to the cause and scale of climate term impact of tectonic plate modern, energy-intensive agricultural
change linked to human ac vi es. So it movements, changes in the solar prac ces.

Variations in output from the Sun A recent study suggested that solar
ac vity may affect ozone levels in the
Energy from the Sun drives the in the middle of the Li le Ice Age. This stratosphere, in turn influencing the
Earth's climate, yet that energy is not me saw observed sunspots fall to weather in the troposphere below.
constant but fluctuates through 11 their lowest recorded number of just a Changes to the jet streams (fast moving
year-long solar cycles. In addi on, few each year, rather than the many winds in the upper troposphere) allow
sunspots which appear as darker areas thousands recorded in other years. large 'blocking’ an cyclones to
on the Sun's surface, form and decay in develop. These large-scale, near
unpredictable numbers through each sta onary high pressure systems allow
solar cycle. winter temperatures to plummet over
Sunspots result from a warping of the Bri sh Isles and Western Europe,
the Sun's magne c field. While exactly as happened during the Li le
sunspots are cooler than other parts of Ice Age.
the Sun's surface, they are associated Those who wish to reject human
with solar flares. These explosions on ac vity as the cause of current global
the surface of the Sun are equivalent to warming point to an increase in solar
millions of atomic bombs. ac vity over the last few solar cycles.
It is s ll not clear how solar ac vity They argue that it is this solar ac vity,
affects the Earth's climate. Some have rather than human-produced
pointed to the fact that the ‘Maunder greenhouse gases, which is the reason
Fig.207 Solar flares.
Minimum’ occurred from 1645 to 1715 behind the rise in global temperature.
Volcanic eruptions ny mirrors, reflec ng incoming radia on Fig.208 Lake Toba, caldera lake, Sumatra.
back into space. This resul ng cooling of
Volcanic erup ons can eject vast the lower atmosphere is known as a
quan es of volcanic ash (powdered rock ‘volcanic winter’.
fragments) into the stratosphere. This ash
74,000 years ago a supervolcano
may be carried around the globe, erupted on the Indonesian island of
reflec ng part of the Sun's radia on and
Sumatra. The explosion le a crater, now
leading to a sudden cooling of the Earth's called Lake Toba, 100km long and 30km
atmosphere.
wide.
The 1815 erup on of Mount
Tambora, on the Indonesian island of One hundred mes larger than the
Tambora erup on, Toba ejected over
Sumbawa, caused a global cooling of the
world's climate. In Europe, thousands of 2,800km³ of volcanic material. 800km³
miles away, intensely coloured sunsets fell as ash, covering much of South East disaster, severely reducing the size of the
and colder temperatures led 1816 to Asia in a layer of powdered rock 15cm planet's human popula on, perhaps to as
thick. The volcanic winter which followed
become known as 'the year without a few as 3,000 - 10,000 people. Human
summer.' resulted in a global cooling of up to 5 C. popula ons in northern la tudes may
The six billion tonnes of sulphur dioxide have been reduced to just a handful. This
Sulphur dioxide is also released
during erup ons. This gas dissolves in ejected may have cooled higher la tudes created a 'gene c bo leneck' by
by up to 15 C for three years. reducing gene c diversity in the surviving
cloud droplets to form fine aerosols of
sulphuric acid. These acid droplets act as The erup on was a major biological human popula ons.

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The climate has changed from the start of the Quaternary period.