Weather Eye with John Maunder

The UN Secretary-General Ban Ki-moon has invited world leaders, from government, finance, business, and civil society to Climate Summit 2014 and this summit will be held this week in New York.

The aim of the conference is to galvanize and catalyse climate action. The Secretary General has asked world leaders to bring bold announcements and actions to the Summit that will reduce emissions, strengthen climate resilience, and mobilize political will for a meaningful legal agreement in 2015. I will summarise the finding of this conference next week.

Meantime, the so called global warming is currently taking a break. Global temperatures rose drastically into the late 1990's, but the global average temperature has risen only slightly since 1998 , which is too many people is surprising, considering most climate models predicted considerable warming due to rising greenhouse gas emissions. Several so called climate sceptics, although I much prefer the term climate realists, have used this apparent contradiction to question many aspects of the climate change story – or at least the harm potential caused by greenhouse gases – as well as the validity of the climate models.

However, the majority of climate scientists continue to emphasize that the short-term warming hiatus could largely be explained on the basis of current scientific understanding and did not contradict longer term warming.

Researchers have been looking into the possible causes of the warming hiatus during the last few years. Reto Knutti, professor of climate physics at ETH Zurich, in Switzerland, has systematically examined all current hypotheses. In a study published in the latest issue of the journal ‘Nature Geoscience', he concludes that two important factors are equally responsible for the hiatus.

One of the important reasons is natural climate fluctuations, of which the weather phenomena El Nino and La Nina in the Pacific are the most important and well known. "1998 was a strong El Nino year, which is why it was so warm that year," says Reto.

In contrast, the counter-phenomenon La Nina has made the past few years cooler than they would otherwise have been.

The second important reason for the ‘warming hiatus' is that solar irradiance has been weaker than predicted in the last few years. This is because the identified fluctuations in the intensity of solar irradiance are unusual at the present time. In general, sunspot cycles each lasted about 11 years in the past, but for unknown reasons the last period of weak solar irradiance lasted 13 years.

Furthermore, several volcanic eruptions, such as Eyjafjallajökull in Iceland in 2010, have increased the concentration of floating particles (aerosols) in the atmosphere, which has further weakened the solar irradiance arriving at the Earth's surface.

For further information a variety of climate matters wee; https://sites.google.com/site/climatediceandthebutterfly/