How to take on the climate sceptics


1. 1998 was an exceptionally warm year (global average) but several
years in the 2000s were very similar, within the accepted margin of
error of the measurements (ie about 0.1 C). It is true that since the
late 1990s, the warming curve has flattened out, but it is totally
untrue that global average temperatures have fallen back. Overall the
2000s were warmer than the 1990s showing that the decadal mean is
still rising (UK Met Office). The sceptics do accept that CO2 levels
are rising but try to de-link this with global warming. They fail to
understand that the temperature curve will not exactly match the CO2
curve year to year (see 2 below). (Temperature data source NASA GISS).

2. The Sun, volcanic activity, changes in ocean currents, etc, etc,
are all factors that must be taken into account when analysing past
data and when trying to model future climate. The radiation received
from the Sun can be accurately measured. Observed solar variability is
not enough to explain observed global warming and in any case, total
solar irradiance peaked about 1960 and has been marginally lower since
- it does not fit the temperature curve. In the second half of the
2000s there has been a deep solar minimum and corresponding measurable
drop in solar irradiance. It is possible that this has been a cause of
the global warming trend flattening in the 2000s.

3. The northern polar ice cap has been consistently retreating (over
and above the annual waxing and waning) over several decades and the
area of sea ice has now been at (very briefly) or well below (most of
the time) the long term average every month since early 2003
(Cryosphere Today; U. of Illinois). In late 2007 the summer melt
reached over 2.5 million km2 below average. The curve has shown signs
of flattening in the last few years, which is consistent with 1 and 2
above, but it is simply untrue that the ice area has recovered in the
arctic. There is also evidence that the ice is thinning, as well as
the area reducing.

For reasons that are not clear yet, antarctic sea ice is not
retreating as it is in the arctic.

4. Sea level is rising as measured at tide gauges and by satellite.

5. The UK has just experienced its coldest winter probably since
1978/9 and northern Europe and large parts of Russia have also been
very cold. Globally, January/February 2010 was the 3rd warmest in 131
years (NASA GISS). Whilst Europe froze, unsually warm conditions were
prevalent over much of the rest of the planet with very high positive
temperature anomalies over Canada and much of the arctic. Most of
South America and Africa were also warm. The Middle East had a very
warm winter. The fact that the UK had a cold winter does not disprove
global warming because (a) the UK is a tiny part of the Earth's
surface and (b) because such comments fail to distinguish between
weather (short terms variations) and climate (30 years averages).
Climate change does not mean that every year globally or locally will
be warmer than the last.

As a final point we should add that good science is about keeping an
open mind and seeking good evidence. We cannot say that it is 100%
certain that the climate change science is completely correct and nor
should we. However, the probability that it is correct is high and the
actual observations do not suggest there is any significant error in
the science.

Sceptics will continue to try and cherry pick "facts" to try and
undermine the science and in dong so confuse weather with climate,
fail to understand the large number of factors that cause climate
variations and fail to understand that climate change is a long term
trend, not a sudden lurch (although there are triggers that could
cause sudden change).

The bottom line is that the atmospheric concentration of CO2, the
chief global warming gas we are changing, is rising relentlessly (now
40% above pre-industrial levels) and it would be one of the biggest
science shocks of all time if that and predicted much higher levels of
CO2 concentration had little or no warming effect as the sceptics