This chapter sets out why we care about the condition of our atmosphere and climate, and presents information on the pressures, state, and trends of the atmosphere and climate in New Zealand.
Our atmosphere and climate – a summary
New Zealand has a temperate climate that supports our natural environment, economy, and way of life. Our climate is naturally variable because of our location in the South Pacific Ocean and our small but mountainous land area. These factors contribute to the extreme weather, such as heavy rainfall and droughts, which often lead to significant economic and social losses.
Although naturally variable, our climate is also changing. The biggest driver of change is the increase in greenhouse gases from human activities, which is causing temperatures to rise. Global net emissions of greenhouse gases have risen 33 percent since 1990. Between 1990 and 2011, New Zealand emitted around 0.1 percent of global emissions. Carbon dioxide is the greenhouse gas that has the greatest impact over the long term with concentrations over New Zealand rising about 21 percent since 1972. Some changes in our climate, glaciers, and oceans are linked to increasing concentrations of greenhouse gases in our atmosphere. New Zealand’s temperature increased around 0.9 degrees Celsius in the past 100 years. Glacier mass in New Zealand decreased about 36 percent since 1978, while sea levels around New Zealand rose between 1.3 and 2.1 millimetres on average annually over the last century.
Rainfall and wind patterns are also expected to change as a result of the ongoing increase in greenhouse gases. However, because our weather is highly variable year-to-year, it is difficult to detect these effects on our climate. So far, we see no clear trends in the data we have analysed for rainfall and extreme weather patterns (eg lightning strikes and three-day rainfall).
A major feature of our atmosphere and climate is our relatively high levels of ultraviolet (UV) light for our latitude. New Zealand has one of the highest rates of skin cancer (melanoma) incidence in the world partly because of our exposure to high levels of UV light. There has been no discernible trend in the total incidence rate of melanoma since 1996.