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Climate change in Hamilton

Jan 30, 2012

Hamilton’s financial challenges with stormwater and flooding appear likely to get worse as the evidence accumulates of escalating climate change and local numbers align with global shifts. While only a couple of 2011 local storms (in July and October) caused damage, globally the last two years have been the wettest on record and generated catastrophic flooding in many parts of the world.

Despite a strong La Nina, 2011 was also the ninth warmest year on record and the 35th consecutive year that average global temperatures were above average. Hamilton temperatures are rising at close to the global average and rainfall amounts have also gone up according to a conservation authority study that examined records for the last 41 years.

The global average temperature increase so far is 0.8°C, while Hamilton’s is up 0.9°C in the period examined by the HCA study. Annual precipitation has only risen a little over an inch per year but more of that has been coming in extreme bursts as predicted by climate change scientists.

In fact, in most respects those predictions are turning out to be underestimations – not surprising given that science demands a high level of proof for forecasts. The arctic ice cap, for example, was originally predicted to melt by 2050, but we now could be headed to ice-free summers later this decade. In 2011, the extent of arctic ice was more than a third less than the average between 1979 and 2000 and was far below that average in every month last year.

While extreme weather-related events continued to batter Asia and Latin America last year, both Australia and the United States were also hit hard. Nearly 60 percent of the US endured either extreme drought or extreme flooding in 2011 and fourteen separate events broke the $1 billion mark in damages. The previous one-year record was eight.

In Canada there was extreme flooding in Quebec, and across the western provinces of Manitoba and Saskatchewan last year. Hamilton recorded 68 mm of rain in a 24-hour period in mid-October, and had a very wet spring but in much smaller daily amounts.

Windsor wasn’t so lucky – setting an all-time record for the wettest year ever during that same October storm that drenched Hamilton. By the beginning of December, it had recorded 1477 mm compared to a normal precipitation total of 844 mm and convincing city councillors to offer a basement flooding subsidy for the installation of sump pumps and backwater valves.

That’s a step taken by Hamilton council in the fall of 2009 and last year the city extended its “protective plumbing program” to all owner-occupied homes connected to the sewer system. It provides up to $2000 in grants and now requires that all new homes include backwater valves.

Carbon dioxide concentrations in the atmosphere now stand at 392 parts per million – exactly forty percent higher than the pre-industrial period level of 280 ppm. The globe passed the maximum safe level of 350 ppm more than twenty years ago, and current concentrations mean temperatures are already guaranteed to climb nearly another degree even if all emissions stopped today.

Locally the unusual January temperatures both conform to predictions and follow an established trend. The HCA study found average winter temperatures have increased nearly twice as fast as the annual rate.

“Average winter mean temperature has increased 1.7°C”, notes the HCA study, while summer averages are only up 0.3 °C, and spring and fall ones have climbed 0.7°C. Precipitation has dropped in the winter season, climbed marginally in spring, and more substantially during the summer months.

In the wake of the study, the HCA board directed their staff in September to develop a climate change strategy for the Authority that is “designed to increase the climate resilience of the watersheds.”

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