Our atmosphere and climate 2017 focuses on climate change and exposure to ultraviolet sunlight. We chose these themes as the focus of this report because scientific evidence shows human activities are causing long-lasting changes to the state of the atmosphere.
The atmosphere comprises a range of gases (including greenhouse gases such as carbon dioxide, methane, nitrous oxide, and water vapour) and minute dust-like particles called aerosols, encircling Earth and held in place by gravity. Combined, these atmospheric greenhouse gases and aerosols help regulate the global climate by contributing to the extent to which the sun’s energy is distributed and stored around Earth or escapes into outer space.
Without any input from humans, the global climate would vary naturally over hundreds to thousands of years as a result of natural variations in atmospheric and ocean circulations and changes in Earth’s orbit around the sun. The natural climate variations, including ice ages, have led to adjustments across ecosystems and the environment. In many instances, such adjustments have occurred gradually, but there have been occasions, many millions of years ago, where rapid changes occurred, resulting in mass extinctions (Barnosky et al, 2011).
Human activities emit additional greenhouse gases and have increased atmospheric concentrations of these gases to unprecedented levels over a period of less than 100 years (as shown in figure 1) (IPCC, 2013). Such a rapid increase is causing the planet to warm faster than ever experienced in the history of human civilisation (at least the past 2,000 years).
Source: Adapted from NASA; data from National Oceanic and Atmospheric Administration. Some descriptions adapted from the Scripps CO2 Program website, Keeling Curve Lessons
Note: This graph, based on the comparison of atmospheric samples contained in ice cores and more recent direct measurements, shows how atmospheric CO2 has increased since the Industrial Revolution.
This graph shows atmospheric carbon dioxide levels over the centuries.
The Climate change chapter focuses on pressures that are changing our atmosphere and climate and what this changing state means for New Zealand.
Exposure to ultraviolet sunlight
The Exposure to ultraviolet sunlight chapter reports on the pressure on Earth’s protective ozone layer from ozone-depleting substances. This is a decreasing pressure as ozone-depleting substances are now well managed internationally and the ozone hole is shrinking. As long as this continues, the ultraviolet (UV) levels that New Zealanders experience will largely be due to natural causes and variation. Understanding our fluctuating UV levels is important for making good decisions about exposure to UV sunlight. We report on the state and changes in New Zealand’s UV levels, which have implications for New Zealanders’ health.