The heat is on

Our climate is changing; with greenhouse gas emissions still rising, the planet is poised to undergo a profound change

Graph 1: Atmospheric carbon dioxide levels at Mauna Loa Observatory (1958-2014)

Concerned about rising carbon dioxide levels, in 1958 US scientist Charles Keeling began recording atmospheric carbon dioxide levels on the Mauna Loa volcano in Hawaii. Despite many challenges, Keeling gathered a remarkable set of data recording a steady rise in carbon dioxide levels – from 316 parts per million (ppm) in 1957 to 384 ppm 50 years later (see Graph 1).

The records even show that annual cycles are linked to seasonal plant growth in the northern hemisphere, as well as the impact of volcanic eruptions and weather patterns such as El Niño.

All change

Going up

Sea levels are rising by about 3 mm every year.

Graph 2: The 'hockey stick' graph: average temperatures (800-2100)

Getting warmer

The ‘hockey stick’ graph (see Graph 2) shows average temperatures over the past 1,000 years, clearly showing recent sudden rises.

The top ten warmest years on record have all been from 1995 onwards, and every year since 2001 has made the top ten.

The hockey stick graph has proved controversial, with some commentators questioning the accuracy of data obtained from tree ring analysis (the system used to plot temperature change throughout history), in which the size of the rings of a tree are measured to see how much it has grown each year (which is dependent on climate). A 2008 version, with many extra data, confirmed the pattern seen in the original analysis.

Graph 3: Projected increases in temperature by 2100.

Variations of the Earth’s surface temperature (1000–2100). Simulations suggest increases of about 1.5ºC and 5ºC, depending on stabilised CO2 levels. Simulations tend to cluster around 2–2.5ºC.

Warmer still

More alarming still are the projections into the future simulated by models of the Earth’s climate.

Going down…

Ocean pH is falling due to increased carbon dioxide dissolving in our seas (acidification); the average ocean pH has dropped by about 0.1 units since pre-industrial times.







About this resource

This resource was first published in ‘Health and Climate Change’ in January 2009 and reviewed and updated in September 2014.

Statistics and maths, Ecology and environment
Health and Climate Change
Education levels:
14–16, 16–19, Continuing professional development