The annual UN Annual Climate Change Summit began in Poland on November 11th and continues until the 22nd. This major international conference is a key stepping stone towards the goal of securing by end-2015 a comprehensive global climate change treaty to take effect from 2020 onward.
The summit has been framed, in part, by the release last month of the Intergovernmental Panel on Climate Change's (IPCC) landmark report. This is the most comprehensive study on climate change ever produced and has reinforced the evidence about our changing global climate. It concludes that patterns of change can only be attributable to growing concentrations of carbon dioxide (CO2) in the atmosphere resulting from emissions from human-related activity.
Governments now have much more complete information to decide in Poland on policies for implementation of technological and economic measures to reduce carbon emissions, and parallel measures to adapt their countries so as to minimise the impact of climate change. The Stern and earlier IPCC economics reports showed that policies of investment in low carbon energy sources and adaptation are feasible economically, provided they are not delayed until massive investments are required.
Previous IPCC technical assessment reports demonstrated how global warming and other aspects of climate change became more significant as emissions of CO2 increased. Despite criticism of their objectivity, the reports have followed the general tenets of scientific research with hypotheses being verified and modified in light of new data and research methods.
In the last IPCC report in 2007, measurements were beginning to show a slowing down in the rate of increase of annual surface temperature averaged over land and sea areas. But trends were also emerging of rapid melting each year of the arctic summer sea ice, and accelerating loss of land ice from Greenland and parts of Antarctica.
For the first time in 2013, the IPCC used more detailed computations to demonstrate connections between climate change and variability of extreme weather events. It was shown clearly how the increasing frequency and severity of these events leads to multiple and more wide ranging natural disasters.
Analysis of the overall global climate system has clarified how increasing concentration of CO2, now twice the pre-industrial value and likely to exceed the present level by three fold during this century, is strengthening 'greenhouse trapping' of outgoing infra-red radiation leading to extra heat in the lower atmosphere. This heat is stored in the atmosphere, land and ocean. With accelerated melting and movement of land ice into the ocean, and thermal expansion of the ocean, estimates for rate of sea level rise during this century are about 3 millimetres/year or greater.
But in the equatorial Pacific, models confirm that the rate of sea level rise is 3 times greater, leading to salt penetration and de-vegetation of coastal areas. It is anticipated that entire populations will have to evacuate by the end of the century.
Another danger from warming atmosphere is that more moisture is carried upwards, strengthening convection in clouds, leading to more intense rainfall events, disastrous flooding and landslides. Rainfall records are being broken year on year (around 200mm/hr now in South East Asia, for instance, whereas the figure was less than 100mm/hr 15 years ago).
The immediate question asked around the world about climate change is whether the yearly average of global surface temperature, which has risen more slowly in the past 15 years, will resume its earlier, higher rate of rise.
The short answer, unfortunately, is most likely 'yes'.
One reason for recent cooling is the slight reduction of solar radiation resulting from higher concentrations of particles in the atmosphere. This resulted from volcanic eruptions during this period, and from growing industrial pollution and burning forests.
Some scientists had also earlier cautioned about the likely variability of global temperature rise, and this has subsequently been borne out. Surface temperatures have been rising over many land areas of the world, especially in the Arctic and the Antarctic Peninsula (where rapid rises of 3C have resulted from changes in wind patterns).
In sub-tropical areas of Asia, Africa and Australia, this has led to record high temperatures, often lasting extended periods, with serious implications for health and agriculture. The temperature rise in many urban areas is double the rural temperature rise in these countries.
By contrast, average ocean surface temperatures rose more slowly and, over about 10 years, have decreased, particularly in South-eastern Pacific where cold deeper water rises and cools the surface over thousands of square miles. The timing of this extended period of 'upwelling' cannot be predicted yet. However, it is clear that over tens of thousands of years, there have been irregular fluctuations, such as the sudden 'El Nino-La Nina' variations in the Pacific climate, which also influence other oceans when they occur.
Because of this historic repeatability, scientists are confident that the global rise in temperature will return to its long term trend. Moreover, with the greater knowledge about geographical variations, it is becoming clear that intense climatic events in areas that have key economic importance, including Asia, can lead to significant impacts on world health and the global economy, as evidenced by crop failures or flooding disruption of industrial centres. This is why regional and national policies are needed to deal with these marked geographical variations.
For some, the IPCC conclusions are proving difficult to understand. In part, this is because the summary for policymakers provides only a single graph to explain the recent yearly variations of global surface temperature over land and sea.
In order that policy makers and the public are not persuaded by sceptics that global warming has 'stopped', there still needs to be more explanation in Poland using IPCC data about the distinctions between land and sea surface temperature variation. Greater clarity as well as greater scientific understanding are needed in Poland if the UN conference is to make progress toward securing a comprehensive global treaty in 2015.