Nova repeats her strawman argument that the recent heatwave is not a sign of global warming.
Climate Scientists go to pains these days to explain that you cannot attribute one weather extreme on global warming, but you will see a higher number of heatwaves as the background climate becomes hotter.
In Australia, we are now breaking hot records three times more often than cold records. It’s simply more likely for heatwave, such as the January one to occur.
Nova doesn’t get math, so instead rambles out 8 “Nova reasons” why the recent heatwave is not because of global warming.
Nova’s “reasons” as follows:
1. It’s the long term trends that matter — not a few weeks of hot weather
No kidding! And with global temperature increasing, the heatwaves will occur more often, the consequences of longer hotter weather has been an increase in seasonal bushfires, many of which have resulted in people losing their house.
2. The “records” we are breaking are pitifully short
True, modern thermometer records are short, yet hot records are being broken three times more often than cold records. The long term trend is warming.
3. If a few weeks of extreme heat suggest CO2 is causing a catastrophe, then don’t a few weeks of Siberian record breaking cold suggest the opposite?
Another strawman argument. No climate scientist says the heatwave is a sure sign of CO2 causing a catastrophe. Paradoxically, the extended cold weather people are experiencing in the northern hemisphere could be caused by the record ice losses in the Arctic, which is being caused by the warmer climate.
For an interesting (and in depth) look at the physics and data, I suggest this video from the author of the peer-reviewed science.
Also from Judith Curry.
Our study demonstrates that the decrease in Arctic sea ice area is linked to changes in the winter Northern Hemisphere atmospheric circulation,” said Judith Curry, chair of the School of Earth and Atmospheric Sciences at Georgia Tech. “The circulation changes result in more frequent episodes of atmospheric blocking patterns, which lead to increased cold surges and snow over large parts of the northern continents.
4. 50C temperatures have occurred all over Australia before, and without any influence by CO2.
As discussed before, the recent heatwave occurred over most of Australia at the same time, not in isolated places in different years.
5. Heatwaves have happened before many times, and there’s no long term increase
Nova looks at the trends of two cities, Melbourne and Sydney and comes to the incorrect conclusion that heatwaves are not increasing. Nova needs to include analysis of the rest of the country, rather than cherry picking two cities. It seems strange that Alice Springs was not analysed, since this was the cherry picked location in a previous post of hers. Perhaps it’s because the data doesn’t fit her biased conclusion.
6. Global temperatures have been increasing for 300 years
Various reconstructions show a Medieval Warm Period, followed by a LIttle Ice Age, the causes of which are obviously natural, the scale of temperature change is less definite than modern global readings.
Whilst scientists do agree that the previous changes are mostly because of nature (some land-use changes from man date back 1,000s of year), this provides us with an ability to estimate the climate sensitivity. Higher changes in temperature due to small natural forcings become an argument for high climate sensitivity, something Nova is keen to avoid.
The natural causes of previous climate change are known not to be causing the current warming. Milankovitch cycles would put us into a very slow cooling trend, the sun spot and irradiance have been quiet and volcanic activity not significant.
By contrast, levels of greenhouse gases have been increasing and are known to cause warming. Multiple studies of attribution lay the blame for recent warming squarely on greenhouse gases despite natural processes having caused previous temperature changes.
7. The world is not warming any faster now that it was 140 years ago
Joanne Nova cherry picks start/end dates to “show” that warming is not accelerating. Cherry picking is an unscientific method that allows you to arrive at a predetermined conclusion. In this case Nova is merely showing that over short timeframes, the rate of increase can be the same as it was decades ago. Natural variability will ensure this will be the case for many centuries into the future, even though the underlying trend continues to rise.
The following graph shows yet another way to view the trends for the early, middle and latter sections, although this does not suit Nova’s argument since the natural variability starts to be obscured when using longer periods to determine the trends.
8. People are mixing up cause and effect. Any cause of warming will … cause heatwaves.
Nova says …
Shock us. Just because the world has warmed does not mean it was caused by CO2. If other things were warming the planet, they would cause heatwaves too. (Possible causes include but are not limited too: the solar-magnetic effect, cloud cover changes, or ocean current shifts. Heck it could be aliens with ray guns… the planet will warm.)
Yes it could be anything making the planet warm which is why scientists look at the possible causes.
And as interesting as it might be to find aliens with ray guns, the evidence shows that the known radiative properties of greenhouse gases combined with the known atmospheric increase of these gases are the most likely cause of most of the current warming, although aliens cannot be entirely ruled out.