Climate change and New Zealand

Last week the Royal Society of New Zealand released a statement on climate change prepared by its expert committee on climate. The statement responds to the public controversy and confusion around climate change and aims ” to make absolutely clear what the evidence is for climate change and anthropogenic (human-induced) causes.”

NZ emissions in 2004

The statement also indicates likely effects of climate change on New Zealand.

It’s worth reading the three page statement. But in part it makes several points.

“There has been an overall upward trend in global surface temperature since the beginning of the 20th Century. Most of the observed global warming over the past 50 years is very likely to be due to increases in greenhouse gas concentrations in the atmosphere”

“Natural factors also cause climate variations. These include changes in the tilt of the Earth’s axis, the shape of the Earth’s orbit, the energy output from the sun, dust from volcanic emissions, and heat exchanges between the atmosphere and the ocean (such as El Niño).”

“Further global changes are predicted. Many impacts are expected to be more costly as time progresses.
Even if the concentrations of all greenhouse gases and aerosols were held constant at year 2000 levels, a further warming trend would be expected for at least several decades, due mainly to the slow response of the oceans.”

Measurements show that

“Present global atmospheric concentrations of carbon dioxide far exceed pre-industrial values dating back at least 650,000 years.

The global increases in carbon dioxide concentration since pre-industrial times are due primarily to fossil fuel use and land use change.”

If no substantial efforts are made to reduce greenhouse gas emissions projections suggest:

• “An increase in globally-averaged surface temperature of 1.1 to 6.4°C by 2100
• A New Zealand-average warming of 0.2 to 2.0°C by 2040 and 0.7 to 5.1°C by 2090. Fewer cold temperatures and frosts, and more high temperature episodes.
• A stronger west-east rainfall gradient (wetter in the west and drier in the east) in winter and spring, and an increasing risk of extreme rainfall as the century progresses.
• Increasing drought risk during this century in areas which are currently drought-prone.
• An increase in New Zealand-averaged sea level of the same order as the IPCC global projections.
• Natural year to year variations in New Zealand’s climate will be superimposed on top of these projected anthropogenic changes.”

However, its not all gloom and doom. The statement indicates that while major international policy changes are required to reduce net emissions of greenhouse gases these can be achieved using existing technologies. The suggested policies include:

• “More efficient use of energy, e.g. better designed and insulated houses, more efficient appliances and industrial processes
• Renewable energy sources, e.g. hydropower, geothermal, wind, marine, and solar
• Lower-carbon fossil fuels such as natural gas and the capture and storage of emissions from power plants
• More efficient transport and urban systems and the use of appropriate biofuels and other renewable energy sources to power transport
• Reforestation, reduced deforestation, and lower emission forms of agriculture”

The members of the RSNZ New Zealand Climate Committee are:

• Dr DS Wratt crsnz (Chair), NIWA Wellington,
• Dr JA Hall mrsnz, NIWA, HAMILTON
• Dr WA Matthews , WELLINGTON
• Dr Brett Mullan , NIWA, WELLINGTON
• Dr Jim Renwick mrsnz, NIWA Wellington,
• Dr PJH Sutton, NIWA, WELLINGTON
• Assoc Prof R Warrick, International Global Change Institute, The University of Waikato, HAMILTON
• Dr SA Weaver , School of Earth Sciences, Victoria University of Wellington, WELLINGTON

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