The World in 2030

The World in 2030 129
But the above researchers’ assumption about clouds
formed by contrails heating up the atmosphere may
be wrong. Some climate scientists have theorised
that aircraft contrails 256 (also called vapour trails) are
implicated in global dimming, 257 but the constant
flow of air traffic previously meant that this could
not be tested.
The near-total shutdown of civil air traffic during the
three days following the September 11, 2001 attacks
afforded a rare opportunity in which to observe the
climate of the United States absent from the effect of
contrails. During this period, an increase in diurnal
temperature variation of over 1°C was observed in
some parts of the US, i.e. aircraft contrails may have
been raising nighttime temperatures and/or lowering
daytime temperatures by much more than previously
thought.
In other words, global dimming may be masking the
effect of global warming but, in doing so, is slowing
down its worst effects. Scientists are not agreed on
this subject. 258
In the end, most environmentalists come to the conclusion
that the growing world population must reduce its use of air
transport, rather than allowing it to grow vigorously as is
predicted. However, I fear that unless high carbon taxes or
even legislation limiting air travel is introduced (something
that would be very difficult to achieve on international
routes) the business community and the general public will
continue to increase its demand for aviation.