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What is the problem with climate change?

It is causing more frequent and worse heatwaves, wildfires, floods, and storms. These impact human health, farming, fisheries, forestry, food security, infrastructure, drinking water supplies, and biodiversity. They cause social stress and have economic costs (including disaster relief, firefighting, lost crops, lost tourism, increased or no insurance cover).

Infrastructure costs include damage and failure of electrical and communication services, sewage treatment, landfills, stormwater drains, roads, buildings, harbours, airports, railway lines.

Biodiversity costs include loss of marine and terrestrial plant production, altered ecology perhaps favouring pest species and pathogens (viruses, bacteria, fungi, parasites), and further declines of threatened species.

These impacts get increasingly severe with more global warming and will affect everyone now and future generations.

Can we prevent climate change from getting worse?

Yes, by reducing its causes, namely the burning of fossil fuels. In addition, increasing carbon storage by vegetation on land and in the sea (e.g., forests, corals, shellfish, plankton that sink to the seabed) will reduce atmospheric carbon dioxide over time.

Can we not use technology to adapt to climate change?

Yes, technology will help, especially by replacing fossil fuel as an energy source with non-carbon emitting sources (e.g. solar, wind, wave and hydro-power). However, technological (e.g., air-conditioning) and infrastructure (e.g., sea walls) adaptations will become more expensive and not protect natural ecosystems or reduce natural disasters (fires, storms).

How much has the world warmed so far?

By just over 1 oC globally since the late 19th century. Warming varies a lot geographically, being greater in the high latitudes of the northern hemisphere and much less in the Southern Ocean. However, New Zealand air temperatures have also warmed by 1 oC from 1909 to 2018.

How much has sea-level risen?

Globally, by 19 cm from 1901 to 2010, an average of 1.7 mm per year. The amount varies geographically due to land level changes and ocean height variation. In New Zealand, sea-level has risen faster, i.e., by an average of 2.4 mm per year from 1961 to 2018 (before 1960 it rose at 1.2 mm/year). In itself this seems insignificant but combined with high tides or storms, it means greater coastal flooding, landscape change and saltwater intrusion into wetlands. In New Zealand, sea level will rise a further 0.2 to 0.9 m (above a 2005 baseline) by 2050 and 2100 respectively.

Is there any good side to global warming?

While there may be, on average, milder winters and less snow, the negatives greatly outweigh the positives. In some locations this may lengthen the growing season in high latitudes, lead to early harvests, and increase decomposition rates. Given good data on trends and understanding of ecosystems, it may be possible for farming and fisheries to adapt to climate change in some areas. However, changes in atmospheric circulation may be resulting in more extreme cold weather in some regions such as northern America and Europe. These extreme events will have negative effects on farming as well as human health.

Although higher carbon dioxide levels can increase plant growth rates this requires more moisture on land and additional nutrients in the sea which are generally not available. Thus a carbon dioxide “fertilisation” effect is unlikely. Ocean phytoplankton productivity is predicted to decline due to climate change.

Why does global warming affect the weather?

Increased temperature results in more energy in the climate system. This manifests in stronger winds, greater evaporation of moisture from land and ocean leading to more clouds and extreme rainfall events, drier land and vegetation, longer droughts and more floods.

Is there any scientific debate about whether global warming (climate change) is happening? 

No. The climate data show it has been happening for decades. A few people deny the role of our burning of fossil fuels as contributing to carbon dioxide and other greenhouse gases in the atmosphere (which is the cause of global warming and predicted decades ago). However, there is no other reasonable explanation for global warming, and carbon dioxide concentrations only make sense when fossil fuel burning is accounted for.

How come the media portrayed uncertainty in whether fossil fuel emissions caused climate change?

There were organised fossil fuel industry supported campaigns to promote uncertainty so as to delay any action to reduce fossil fuel use. This strategy has been called the “tobacco playbook” following the success of the tobacco industry using naive, mistaken, poorly informed and compromised scientists to debate whether smoking was harmful. This debate suits the media need for controversy and provides a convenient excuse for people who do not want to change or have new regulations that affect their lifestyle. A nice rebuttal of the arguments against anthropogenic climate change is available on Skeptical Science.

Further reading

For the world: IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp. Also available at

For New Zealand: Ministry for the Environment. 2020. National Climate Change Risk Assessment for Aotearoa New Zealand: Main report – Arotakenga Tūraru mō te Huringa Āhuarangi o Āotearoa: Pūrongo whakatōpū. Wellington: Ministry for the Environment.

A nice overview regarding New Zealand “Our atmosphere and climate 2020 summary“.

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