London, UK - Ahead of the latest
UN talks on climate change in Mexico, a UK Met Office analysis of
long- and short-term trends in climate reveals that the evidence
for man-made warming has grown even stronger in the last year.

There is overwhelming evidence of warming in a wide range of
climate indicators, not just surface temperature. The picture for
short-term trends is more complicated. Short-term variations are
affected by natural variability and other factors as well as
long-term warming.

In the last 10 years the rate of warming has decreased whilst
the rate of loss of sea-ice extent has increased - an apparent
contradiction - the Met Office’s latest analysis of the science
shows that this is entirely consistent with our understanding of
how the climate behaves and with our model projections.

In providing the evidence of continued warming and drawing from
the work of more than 20 institutions worldwide, the Met Office
Hadley Centre compiled results for a range of climate indicators -
not just surface temperature. The multiple data sets used for each
indicator are from diverse sources such as satellites, weather
balloons, weather stations, ships, ocean buoys and field
surveys.

Dr Matt Palmer, an ocean observations specialist at the Met
Office, said: “It is clear from the observational evidence across a
wide range of indicators that the world is warming. As well as a
clear increase in air temperature observed above both the land and
sea, we see observations which are all consistent with increasing
greenhouse gases.”

These changes include:

• Increases in water temperature at the sea surface down a depth
  of hundreds of metres.



• An increase in humidity as a warmer atmosphere holds more
  moisture.



• Increases in sea level as warmer waters expand and land-ice
  melts.



• Shrinking of Arctic sea-ice, glaciers and Northern Hemisphere
  spring snow cover.

Since the late 1970s the long-term rate of surface warming has
been about 0.16 °C per decade. However, over the last decade the
rate of warming has decreased.

Natural variability within the climate system could explain all
of this recent decrease. Other factors could have contributed.

• Changes in stratospheric water vapour



• Solar variability



• Increased aerosol emissions from Asia

The rate of warming has been underestimated in the last decade
because of:

• changes to sea-surface temperature measurement practices;



• strong warming in the Arctic - where there are fewer
  observations.

Dr Vicky Pope said: “Our analysis confirms that the signals of
warming are as strong as they ever have been. Improving our
understanding of the factors that affect short- and long-term
trends is helping us to improve our predictions of the future,
helping others to make choices on mitigation and adaptation
providing a more resilient future.”