Apart from bubbles of heat surrounding big cities, the thermometers and satellites of the world have not shown a warming trend for 17 years. This is in spite of some inspired fiddling with the records by those whose jobs, research grants and reputations depend on their ability to generate alarming forecasts of destructive global warming.

To explain this absence of warming in the atmosphere, the warmists now claim that “the missing heat is hiding in the deep oceans”.

This sounds like a water-tight alibi, unlikely to be disproved because of our inability to measure “average ocean temperature” directly.

However the ocean itself is a huge thermometer – all we have to do is to read the gauges.

All liquids expand when heated, and this property is used in traditional thermometers. They have a glass reservoir filled with liquid mercury and a graduated scale to measure any thermal expansion of that liquid.

Oceans have the essentials of a global thermometer – the huge ocean basins are the reservoir, sea water acts like the mercury, and tide gauges on the shore-line (or satellites) measure changes in sea water volume.

Two factors, both dependent on global temperature, are the main causes of rising sea levels – how much ice is melted from land-based ice sheets like Greenland and Antarctica, and the expansion of sea water volume as ocean temperature rises.

Therefore average sea levels are sensitive and accurate indicators of trends in average global temperature.

Historically, sea levels (and global temperatures) rose steeply as the great ice sheets and glaciers melted and Earth emerged from the last ice age. Sea levels rose by 130 metres in just 10,000 years but they have been relatively stable for the last 7,000 years. 

The sea level thermometer was higher than today during the Roman Warm Era, and lower than today when the Little Ice Age ended about 160 years ago. There is no unusual spurt in recent years, proving conclusively that there is no significant extra heat going into the deep oceans, and no global warming hiding there.