Climate Change
» Temperature change over the past 400,000 years
» Past & Present Carbon Dioxide Levels
» Another Greenhouse Gas: Methane
Worldwide, our climate is changing. Changes include increasing temperatures, rising sea levels and a greater incidence of extreme weather, such as storms, heat waves, droughts and floods. Much of this change is a result of human activities that increase the level of greenhouse gases in the atmosphere. Scientists expect that the world will continue to warm over the next 100 years. However, global warming can be slowed if enough countries take action.
'Climate change is a global challenge. If left to run its course, climate change will have significant impacts on our economy, our environment and our society. Scientific evidence now clearly signals the need for action.'
Hon Pete Hodgson Minister for Research, Science and Technology.
Landcare Research's research on reducing greenhouse gas emissions from the terrestrial biosphere underpins New Zealand's ability to measure and monitor its emissions to internationally accepted levels of accuracy, and provides knowledge and technologies to support management practices that reduce emissions.
Temperature change over the past 400,000 years
This graph depicts changes in average global temperature changes over the last 400,000 years. As you can see, the earth's climate has change enormously. During the coldest periods, 8 ºC colder than the present, large areas of North America and Europe were covered with ice over 1 km thick! Only 20,000 years ago this ice extended to places like New York City. The short warm periods are called interglacial periods, while the longer cold periods are called glacial periods.
Temperature Change - Past 100 Years
The following diagram shows observed temperature changes during the twentieth century measured at various monitoring stations around the world. Climate models can reproduce observed global average temperatures quite well, indicating a good but as yet incomplete understanding of the processes resulting in these changes.
Past & Present Carbon Dioxide Levels
Scientists have measured atmospheric carbon dioxide (CO2) concentrations dating back to 400,000 years ago by measuring air bubbles trapped in Arctic and Antarctic ice. High CO2 concentrations occur during interglacial periods (warm) while lower CO2 concentrations occur during the much longer glacial periods (cold). This observation fits with our general understanding that CO2 is a greenhouse gas-- a gas that traps heat and therefore warms the earth. This graph ends prior to the industrial period, when human fossil fuel burning began to change atmospheric CO2 concentrations, but we can see that we're already in an interglacial period (CO2 was relatively high).
CO2 concentration is approximately 370 ppm. Carbon dioxide emissions have accelerated considerably as a result of industrial emissions over the last 100 years, and these emissions have changed the atmospheric CO2 concentration from ~280 ppm to 370 ppm.
Carbon Dioxide Levels - Past 1200 Years
This graph depicts Carbon Dioxide concentration, recorded from different high-resolution Antarctic ice cores, for the past millennium. Atmospheric CO2 concentration fell by about 8 to 10 ppm during the Little Ice Age (from 1280 to 1860). A slight contemporaneous increase in atmospheric CO2 has led to the suggestion that this effect was caused by enhanced carbon storage on land.
Another Greenhouse Gas: Methane
Scientists have also measured atmospheric methane (CH4) concentrations from the same 400,000 year long ice core records. Methane is also a greenhouse gas, and shows similar trends to CO2, including a recent increase to levels not seen over the past 400,000 years as a result of human activity.
Methane Levels - Past 1000 Years
This graph depicts the change in CH4 abundance determined from ice cores, firn, and whole air samples plotted for the last 1,000 years. The atmospheric abundance of CH4 has increased by about a factor of 2.5 since the pre-industrial era as evidenced by measurements of CH4 in air extracted from ice cores and firn. This increase still continues, albeit at a declining rate.