Climate Change - a quick guide

Main Climate Page

This page is a precis of the main climate page.

Greenhouse gases

  1. The sun heats the earth and the earth heats the atmosphere by conduction, convection and radiation.
  2. Of these, radiation is the greatest effect with the heat being absorbed by gases in the atmosphere – the so-called greenhouse gases..
  3. These gases are water vapour (H2 O), carbon dioxide (CO2), methane (CH4), and ozone (O3). Notable industrial gases are nitrous oxide (N2O) and haloccarbons (CFCs) . CO2 and CH4 occur naturally and are closely, causally related.
  4. Although there is far less CO2 than water in the atmosphere, it absorbs around 40% as much heat as H2 O.

Observed facts

  1. Since the late 19th century, instrumental records show that the warmest 10 years on record have all been since 2000, seven have been since 2010. The warming trend over the last 50 years is nearly twice that for the last 100 years. Every country has warmed significantly.
  2. In the CE, using proxy data such as tree rings and ocean sediments, statistical techniques show that, “The largest warming trends at timescales of 20 years and longer occur since the second half of the twentieth century.”
  3. Sea levels are rising at an accelerating rate. For example, “The sea level around Charleston, South Carolina, has risen by 10 inches since 1950. Its speed of rise has accelerated over the last ten years and it is now rising by about 1 inch every 2 years.”
  4. Yearly numbers of hurricanes show no discernible trend but they are becoming more powerful. There were 26 major (category 4 and 5) Atlantic hurricanes between 1900 and 1919 and 67 between 2000 and 2019. The US National Hurricane Center has been considering the need for a category 6.
  5. The US National Snow and Ice Data Center reports that Greenland and Antarctic ice sheets are melting at increasing rates.
  6. The major greenhouse gas of concern, CO2, has now reached concentrations, over 410 parts per million, levels last seen millions of years ago when temperatures reached 8 or 9 degrees Celsius higher than at present and sea levels reached 10s of metres higher.
  7. By 2100 at the current rate of rise, CO2 concentrations will be double the highest values in the 800,000 year period up to the industrial era.

Items 1-6 are in line with climate model simulations and predictions.


Some island nations are already threatened with flooding. Major coastal cities that could be wholly or partly under water at high tide include London and New York as well as many more immediately threarened such as Mumbai, Osaka, Amsterdam, Miami, New Orleans, Shanghai. Some 200 million or more people now live in areas that will be flooded by 2100 if we take no action. Arguments about apportioning blame and concern about economic impacts of adaptation and reducing carbon emissions pale into insignificance.

We sailors are seeing the effects at first hand with unusually variable and unseasonable weather. As well as tropical storms, we are seeing other extreme events such as Medicanes. However, impacts on our activities now are trivial compared to the predicted future.

The future – COP25

Noting the increasing land ice loss over Greenland and the Antarctic, there is good reason to believe that these trends will continue. It is my belief that delays in facing up to the problems are putting our grandchildren in serious jeopardy. That is a fact seemingly lost on world leaders at the climate conference, COP25 in Madrid last December. They failed to recognise the urgency and, again, deferred decisions.