NZCPR.COM, 10 July 2016 By Brian Leyland
Many articles in the Herald over the past few years have emphasised the dangers of man-made global warming (aka “climate change”) and warned us that extreme measures are needed to save us from this imminent climatic disaster. Almost without exception, the authors of these articles have assumed that man-made carbon dioxide causes dangerous global warming, rapid sea level rise and more floods, droughts, cyclones and so on.
But what does the evidence tell us?
Regarding world temperatures, historical records from ice cores tell us that it was warmer during the Mediaeval Warm Period, the Roman Warm Period and the Bronze Age. The Mediaeval Warm Period was experienced all over the world including Australia and New Zealand.
The oldest set of recorded temperatures comes from central England and started in the mid 1600s. They show a temperature rise of a little more than 1°C – which is not surprising as the record started in the middle of the Little Ice Age. Since 1900 – which was fairly cold – most temperature records show that the world warmed quite rapidly up until the 1940s, then the temperature declined until 1975 when it rose again at the 1930s rate until about 2000.
Since the 1970s, satellite measured temperatures which, NASA says, are the most accurate, have been available and, if the two El Nino events are ignored, show no statistically significant temperature rise for the last 18 years. By contrast, the computer-based climate models predicted temperatures about 0.5° higher than they really are and the IPCC has admitted that 97% of its temperature predictions were much higher than actual temperatures. Should we believe the evidence or the models?