In 2020, the Ontario Ministry of Environment commissioned a study by the Climate Risk Institute, called the Provincial Climate Change Impact Assessment (PCCIA), to predict effects of climate change on several aspects of the Ontario economy, including agriculture and food, for the remainder of this century. The resulting report was submitted to government in January 2023 and made public in August.

The 505-page report, plus appendices, represents lots of work and contains valuable information. However, in my view, its key conclusions about expected climatic effects on Ontario agriculture and food are seriously flawed. The following commentary explains why.

The report concludes, with respect to agriculture and food, “any potential opportunities [from warming climate] are likely to be offset by negative impacts, resulting in declining productivity, crop failure, and livestock fatalities. Several commodities, particularly in the southern regions of the province, are expected to face ‘very high’ climate risks by the end of the century.”

And also, “The assessment results indicate that field crop risk profiles across all regions of the province will be ‘high’ or ‘very high’ by the end of century.”

I have reviewed sections of the report relevant to agriculture and food (including sections on project methodology, overall climate projections and several appendices), and believe that there are three reasons for treating its conclusions with deep caution – indeed skepticism.

First, the report’s analyses depend very heavily on the extensive Assessment Reports (AR) produced every 5-10 years by the International Panel on Climate Change (IPCC) – and specifically the AR5 reports produced in 2013-2014.

However, in April 2021 Working Group 1 (WG I) of the IPCC released the AR6 version of its important Physical Basis of Climate Change, which contains essentially all of the global IPCC information pertinent to the PCCIA study. The WG I report was followed by release of corresponding reports by WG II and WG III, the last release in early 2022.

Although the IPCC AR6 reports were available many months before the PCCIA was completed (16 months in the case of WG I), the changes IPCC made were mostly unused in the PCCIA analyses. PCCIA authors defend this decision by stating that AR6 does not negate their conclusions based on AR5. Yet, many of the changes in AR6 are substantive – both in data provided as well as in the detailed analyses. (See here.)

Given the length of time between release of the AR6 reports, and the release of the PCCIA in January 2023, I believe that team should have made more effort to base their analyses on current IPCC data and perspectives.

The second weakness is much larger. The IPCC uses groups of climate models to envision what climate might be like in remaining years of this century.  Details are complex but, in general, the models differ based on amount of global heating to be caused by humans. There are models that involve assumptions of very low and low heating (average of ~2 Watts/m²), medium heating (~4.5 W/m²), high (~7 W/m²) and very high (8.5 W/m²).

When AR5 was written, the 8.5 W/m² heating option was considered very high but still quite plausible. However, as scientific knowledge advanced and AR6 reports were being written, the likelihood of 8.5 W/m² came to be considered much less plausible. For a detailed, informed discussion on this, see here. Of particular note, in background documents that the UNFCCC (United Nations Framework Convention on Climate Change – the parent of IPCC) published in 2021 and 2022 for use at international climate conventions on climate change, the 8.5 W/m² scenario does not appear to be even mentioned. By contrast, these documents show that 4.5 W/m² model calculations match quite well global temperature expectations, including corrective measures now being implemented by governments and industry worldwide.

In producing the PCCIA, the Climate Risk Institute completed extensive analyses using both the 4.5 W/m² – that it labels as a “low (or sometimes “lower”) emission pathway” – and the 8.5 W/m² option that it labels “high emission pathway.” The PCCIA also refers the 8.5 W/m² option as “business as usual” (Appendix 4) – which as numerous informed authorities have pointed out, it definitely is not.

More critically, despite completing comparable, parallel analyses for both the 4.5 and 8.5 analyses, the PCCIA document reports mainly – and in many cases only – the 8.5 W/m² results. I don’t understand why.

If the writers’ objective was to present a worst-case perspective, that might make sense. But to portray it as probable – indeed, “business as usual” – while mostly marginalizing model 4.5 W/m² results is in my view selective and misleading. For a much more detailed commentary/analysis on this by a credible climate scientist, see here – a commentary that was published, by the way, in 2020, likely before the PCCIA study was started.

My third point involves the reasonableness of the report’s conclusions about late-century climatic effects on Ontario agriculture. The report states that the 8.5 W/m² climate change models predict no notable increases in drought stress in Ontario; expected increases in precipitation match increases in evaporative demand. The PCCIA 8.5 analyses do predict an increase in the number of very intense one-day (but not three-day) localized rainfall events. However, the major predicted effect is an increase in the number of summer days with maximum temperatures of above 30C – which the report labels as ‘extreme heat.’ Because of this, it projects major future reductions in the productivity of many Ontario crops including corn, soybeans and winter wheat.

IPCC AR6 WG I models estimate an average 4.4C increase in average global temperature by the year 2100 with 8.5 W/m² increase in global heating. By coincidence, that corresponds almost exactly to the difference in average July daily maximum temperature between Woodstock, Ontario and St. Louis, Missouri.

But present-day farmers in Southern Illinois (across the Mississippi River from St. Louis) have no trouble producing good corn, soybean and wheat yields with their high number of above 30C maximum temperatures! In fact, the average daily maximum in July in St. Louis is 31.6C, meaning the majority of days in July now exceed 30C. The Mississippi Delta, where soybeans are grown extensively and successfully, is hotter still.

So, bottom line:

There is an abundance of information showing that high net GHG emissions are likely to cause problems for humans globally. Ontario and other Canadian farmers should do their part to reduce net GHG emissions where this can be done without seriously affecting food output and farm family income. However, I’d recommend not using results of the 2023 Provincial Climate Change Impact Assessment provide realistic projections on what the climate holds in store for Ontario farm production in the remainder of the twenty-first century.