Global warming and its implications certainly constitute a hot topic for discussion and argument round the world. Talkback sessions and letters to the editors of newspapers are full of comment about this hot topic. Some of the opinions expressed are ill-informed showing ignorance of scientists' views, and many reveal disturbing uncertainty about the future, the possible effects of global warming and when we are likely to feel the impact of climate change.

The other aspect of discussion is what we can do to slow the warming and if or when we need to act.
"Is anything we do going to be of significance when we are such a small country?"
"How will changes affect our agricultural economy?"
How can our industrial and business interests be served if there is a limitation on our use of carbon producing fuel?"
"Why should these prophets of doom and scaremongers be believed? There has been climate change before without disastrous results."
"Shouldn't we wait until we understand climate science better before we take any inconvenient steps towards changing our greenhouse gas emissions?"

Gareth Renowden in his book Hot Topic: Global warming and the future of New Zealand, has provided thoughtful science-based explanations and comment on these issues and related them to the New Zealand situation. He outlines the key science findings on climate change summarised in the recent Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC). He highlights for us the importance and relevance of these findings by relating them to New Zealand conditions and by commenting as a climatologist with access to exciting resources through the Internet and as a small farmer with local knowledge in New Zealand. He states his intention of presenting his material without being influenced by political issues or the business interests of those companies making huge profits out of supplying or burning fossil fuels and seeking to deny that the problem exists.

In the first three chapters Renowden sets out clearly the scientific background to the issues. He stresses that what may seem a small rise in average temperature, a rise of two degrees can result in considerable climate change - differing in its impact in different areas. The Poles will experience more change as a result, especially the Arctic region.

To those who downplay the importance of any changes we can make because we are such a small country, he says that while there is some truth in that comment it is of vital importance to us that there is a worldwide recognition of the problem and a concerted effort to counteract it.

He writes, "The international progress we've already achieved, from the United Nations Framework Convention on Climate Change to the Kyoto Protocol, may not be universally popular, but is an important step down that road."

Another argument for taking all possible steps to reduce carbon emissions is that New Zealand's cooperation with the rest of the world on climate change will be an important factor in maintaining good trade relations internationally.

In the fourth and fifth chapters Renowden looks at the possible impact of climate change on New Zealand and concludes with stressing that small shifts of climate can mean big changes at ground level. He comments on the change already noticeable in mountain vegetation as the snowline moves further up the mountains. It may seem wonderful news that the climate in the south of New Zealand may warm enough for crops which at present can be grown only in Northland to flourish in the south, but it must be remembered that weeds and pests would also flourish in the south.

Droughts would also become more frequent and severe in drought-prone areas and the lack of water for irrigation would impact badly on the increasing number of dairy farms. Another issue facing the dairy industry is how to manage its emissions of methane and nitrous oxide.

Later chapters look at the wider picture – first the impact of global change on our Pacific neighbours and then on other countries. Examples, diagrams and photographs highlight the points stressed.

Appendices include:
The Sceptical View in which the arguments of the sceptics are set out and rebutted with scientific evidence
Notes and resources
List of acronyms
Glossary
Acknowledgements
Index

The flap of the back cover has a clear coloured map showing climate change impacts on New Zealand.

I strongly recommend everyone to read this book, but especially recommend it to those who make decisions on action to counter the impact of global warming and those who are able to influence the thinking of others on this issue.

Hot Topic: Global warming and the future of New Zealand by Gareth Renowden
Published by AUT Media 9 August 2007
ISBN 978-0-9582829-0-1
Designed by HB Media
Edited by Bradstock & Associates, Christchurch
RRP NZ$24.99