Many factors affect the atmosphere and climate – both human-caused and natural. This section presents our latest findings on human-caused pressures (global emissions of greenhouse gases and ozone-depleting substances) and natural pressures (ocean conditions and climate oscillations).
This section sets out the main human-caused pressures on the atmosphere: emissions of greenhouse gases and ozone-depleting substances.
Global emissions of greenhouse gases are still increasing
Human activities – mainly the burning of fossil fuels – have led to increased concentrations of greenhouse gases in the atmosphere. Between 1990 and 2011, global net emissions rose 33 percent (see figure 13).
Over this period, New Zealand emitted around 0.1 percent of global emissions. By comparison, the United States contributed an average of 16 percent, and China 15 percent.
Note: The United Nations Framework Convention on Climate Change is the preferred data source, but because some countries do not report on all years since 1990, the data are supplemented with Climate Analysis Indicators Tool data. The effect of the various greenhouse gases are combined into one indicator, known as CO2 (carbon dioxide) equivalent.
This graph shows the estimated net emissions of greenhouse gases by major emitting countries (United States of America, Russia, rest of the world, Japan, Indonesia, India, European Union, People’s Republic of China, and Brazil) between 1990 and 2011. Visit the MfE data service for the full breakdown of the data.
New Zealand’s net greenhouse gas emissions increased 42 percent between 1990 and 2013 (see figure 14). Emissions from agriculture was the largest contributor at 48 percent (mainly methane emissions from cattle and sheep), followed by emissions from energy production, at 39 percent.
Note: Mt C02 equivalent – megatonnes equivalent carbon dioxide.
This graph shows the net emissions of New Zealand greenhouse gases between 1990 and 2013. Visit the MfE data service for the full breakdown of the data.
Ozone-depleting substances drop to 2 percent of 1986 values
Globally, the production of ozone-depleting substances has decreased to 2 percent of their 1986 values. Atmospheric ozone is important as it absorbs harmful ultraviolet rays from the sun. Emissions from chlorofluorocarbons and other ozone-depleting substances have caused a hole to open in the ozone layer above Antarctica. While this ‘ozone hole’ has little effect on UV levels in our atmosphere, filaments of ozone-poor air can sometimes pass overhead when the ozone hole breaks up in spring.
The Montreal Protocol on Substances that Deplete the Ozone Layer, agreed in 1987, led to a decrease in the production of ozone-depleting substances. This decrease is expected to reduce the size of the ozone hole to pre-1980 levels by around the middle of this century (United Nations Environment Programme Ozone Secretariat, nd).
For more detail see Environmental indicators Te taiao Aotearoa: Global emissions of ozone-depleting substances.
This section presents information on two natural pressures on our climate: oceans and climate oscillations.
Oceans influence our climate
The oceans influence our climate through the exchange of heat and moisture between the ocean and the atmosphere. For example, the oceans provide much of the heat that drives tropical cyclones, which are a significant influence on New Zealand’s weather.
The oceans also moderate the effects of climate change by absorbing carbon dioxide and heat from the atmosphere. However, absorbing carbon dioxide makes oceans more acidic (Ciais et al, 2013).
For more information see: Marine chapter.
Climate oscillations can affect our climate
Climate oscillations are natural variations in the world’s climate patterns. Three of these have a particular influence on New Zealand’s weather patterns – the El Niño Southern Oscillation, the Interdecadal Pacific Oscillation, and the Southern Annular Mode.
The El Niño and La Niña phases of the El Niño Southern Oscillation influence New Zealand’s temperature and rainfall. El Niño can lead to droughts in the east of New Zealand, while La Niña can lead to flooding in the north (NIWA, 2007).
For more detail see Environmental indicators Te taiao Aotearoa: Climate oscillations.