A 135 year temperature record

In 1858, the Royal Navy commissioned a wooden sailing ship known as the HMS Challenger. She served admirably in military operations, including in the waters around Australia, for more than a decade. But in the 1870s, this ship would chart a new course and reshape the world of science.

In 1870, the ship was given a new task; it would undertake the world’s first long-duration marine science expedition. The guns of the ship were stripped off and replaced by beakers and scientists.

From December, 1872 to May 1876, the ship sailed almost 115,000 kilometers (69,000 miles), covering the oceans of the Earth. As it went, it stopped at over 360 locations. They measured the depths of the ocean, took samples of the water, measured the weather, the temperature and the salinity of the water, and even took biological samples.

This voyage helped build our basic knowledge of the ocean floor; the mountain ranges and the trenches, the types of life found in the deep. As the first real marine-science cruise ever, its legacy lives on today in the operations to observe and understand the oceans.

Remarkably, its data is still helping science today. The researchers on the Challenger measured temperatures throughout the ocean on their voyage. If researchers make measurements of temperatures today, the data of the Challenger mission is precise enough to allow for creation of a 135 year temperature record.

The temperature difference in these measurements is consistent with other data suggesting that the oceans have taken up about 90% of the extra heat built up due to excess atmospheric carbon over the last century+.

This long temperature record allows for new discoveries as well. They allowed researchers to construct estimates of the change in ocean volume due to thermal expansion (materials getting bigger as they heat up). 40% of the sea level rise between 1873 and 1955 was found to be from thermal expansion (with groundwater pumping and glacial melting making up the remainder).

The warming in some parts of the deep ocean is also greater than expected. The Eastern Pacific ocean, a key area in global climate due to the El Nino cycle, was found to have warmed more rapidly than found by other data sets, a finding which will be key to understanding the impacts of climate change on the El Nino cyclicity.

The climate change signal, of course, shows up everywhere these days, even in places that are surprising. Just as interesting though is the use of the data set; the Challenger was the type of voyage that set the basis for a century of discovery, and its data is of such quality that it can still be used today. Via Timeline Photos.