Canadian Underwriter

Why climate change might be worse than you think

June 21, 2019   by Greg Meckbach

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If you are using today’s climate models to predict the frequency and severity of tomorrow’s severe weather, your estimates could be off, suggests a recent convocation speaker at a major Canadian university.

Recent unusual patterns in the jet stream are “tied to some of the most damaging extremes we have seen in recent years,” said Michael Mann, an atmospheric science professor at The Pennsylvania State University, in an interview Friday. He cited Hurricane Harvey as an example.

“We also know the climate models, at least not currently, are not able to capture accurately the underlying atmospheric physics that’s responsible for that behaviour,” added Mann. “Why that’s important [for the Canadian property and casualty insurance industry] is it is leading to what we argue is an underestimate of the impact that climate is already having on these damaging weather extremes.”

Mann was the convocation speaker June 13 for the faculty of science at McMaster University in Hamilton.

There is some uncertainty over how frequent severe rain will be in the future, in Canada, compared to today, Mann told Canadian Underwriter Friday.

“It is sort of a one-side uncertainty, which is to say we are fairly confident that [climate] models must be underestimating the rise that we will see in these persistent weather extremes.”

Global warming means Canada will have more frequent heat waves, droughts and precipitation events, Insurance Bureau of Canada CEO Don Forgeron said Apr. 25 at IBC’s annual general meeting.

Scientists expect certain types of extreme weather events to become more extreme in the future because if the atmosphere gets warmer, it can hold more moisture, said Mann.

To find out how this could affect weather, climate scientists use models and run them both with and without the factor of increasing concentration of greenhouse gases in the atmosphere.

Scientists can see how often an extreme event happens in a “control” model – which does not factor in an increase in greenhouse gas emissions, said Mann. They can then – compare that to how often the same event happens where there is an increase in GHG emissions, added Mann, who is also director of Penn State’s Earth System Science Center (ESSC), where researchers make models of the Earth’s climate system.

“You can say, ‘climate change made this event two times more likely, for example. We would argue that those attribution studies are underestimating the impact that climate change has had – the degree to which the various types of extremes have become more frequent.”

This, Mann suggests, is because many climate models are not fully accounting for recent patterns – known as quasi-resonant amplification – in the jet stream, which NASA describes as a belt of westerly winds in the northern hemisphere.

What is unusual is the amplitude – or the distance from the ridge to the trough – in the jet stream.

If you look at a map depicting the jet stream, the ridge is where the jet stream bends north and curves back around to go south. The trough is where it goes south and bends back north.

An unusually large amplitude was associated with some extreme weather events in both the United States and Canada in the summer of 2018, said Mann. What also happened was the extreme weather stayed in the same area a long time.

The mechanism is fairly complicated, Mann explained.

“Current generation climate models don’t resolve that mechanism very well. The models are not run at a high enough spatial resolution to resolve some of the underlying atmospheric processes that are important to this phenomenon.”

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4 Comments » for Why climate change might be worse than you think
  1. Balter Hengstler says:

    This is because, despite the best efforts of the climate eschatology department and the compliant media, weather is not related to climate.

  2. John Branscombe says:

    There are 2 things that are rarely mentioned in this discussion and both should cause us concern.

    First, if the CO2 being dumped into our atmosphere by us was suddenly cut to zero completely, the average global temperature would continue to rise for many years before stopping and starting to fall. The “greenhouse effect” would not be “gone”.

    Secondly, if global temperature rise was halted in its tracks at current levels, the sea level will continue to rise. Glaciers and ice caps would continue to melt at current rates and the thermal expansion of the ocean water would continue to happen as atmospheric heat continued to be transferred to the seas.

    Both of these should be kept in mind while some continue to deny the reality we face.

  3. Walter Horsting says:

    Canada and Northern countries need to worry about sun cycles 24-27 ushering in the 400-year grand solar minimum cooling that will move the crop line south by 100-300 miles.

    Greens save nature from RE industrialization, do the Math, by 2050 we need 3-5 cubic miles of oil equivalents; or 12 to 20 Billion solar rooftops, 9 to 15 million turbines or just 4 container ships of the 20′ 30-ton shippable MSR:

    Save nature from Massively unsustainable RE:

  4. Robert Muir says:

    Yet our Environment Minister Catherine McKenna writes On June 13, 2019 that “”the observational record has not yet shown evidence of consistent changes in short-duration precipitation extremes across the country”, and previously Environment Canada scientists published in Atmosphere-Ocean “single station analysis shows a general lack of a detectable trend signal” Canadian Underwriter has previously checked statements made by the insurance industry and found no support for increased storm frequency claims concluding with this:
    “Associate Editor’s Note: In the 2012 report Telling the Weather Story, commissioned to the Institute for Catastrophic Loss Reduction by the Insurance Bureau of Canada, Professor Gordon McBean writes: “Weather events that used to happen once every 40 years are now happening once every six years in some regions in the country.” A footnote cites “Environment Canada: Intensity-Duration-Frequency Tables and Graphs.” However, a spokesperson for Environment and Climate Change Canada told Canadian Underwriter that ECCC’s studies “have not shown evidence to support” this statement.”
    The CBC Radio-Canada Ombudsman has also recently weighed in on this topic of reported storm intensity concluding that CBC failed to meet its own standards of journalistic practice fro accuracy and impartiality:
    McMaster researchers have also predicted less extreme future storms in southern Ontario:
    Which is consistent with observed trends in the national Engineering Climate Datasets – those show 42% more decreasing trends than increasing ones in southern Ontario:
    It would be great to have Canadian Underwriter acknowledge the position of our Environment Minister and scientists in her department, as well as research on future climate from McMaster University.

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