by

Indur M. Goklany

We are constantly bombarded with claims that weather-related events will get worse over time, at least in part because of global warming. So one should expect that aggregate deaths and death rates due to weather-related extreme events worldwide would have trended upward in recent decades.

But do they?

The following bar chart shows (approximate) aggregate trends in these critical measures between 1900 and 2004 for "weather-related extreme events", namely, droughts, extreme temperatures (both extreme heat and extreme cold), floods, landslides, waves and surges, wild fires and wind storms of different types.[1]

Yes, there is a trend here, but is it upward?

This, of course, begs the question as to why, if the globe is warming, matters aren't getting worse?

Curves like this illustrate that due diligence requires that analyses and/or claims of future impacts should be accompanied, at a minimum, by checks of whether their future projections match with past reality. Of course, as your mutual fund advisor will tell you, "past results are not necessarily indicative of future performance." True, but one should have to reconcile the two, matching the past and the present with the future. And this goes not just for impacts (e.g., deaths and death rates) but also assumptions that feed into impacts assessments. For example, how reasonable is an assumption of 1 percent growth per year in carbon dioxide concentrations when historically it has averaged 0.40 percent per year from 1959 to 2004, during which period it only once exceeded 0.75 percent (year-to-year increase)?

Notes
[1] DATA SOURCES: For deaths: "EM-DAT: The OFDA/CRED International Disaster Database," available at http://www.em-dat.net, Université Catholique de Louvain, Brussels, Belgium; for population: from 1900-1925, McEvedy, C. and R. Jones, (1978), Atlas of World Population History, New York, Penguin; from 1950-2004, World Resources Institute, "Earth Trends," available at http://www.wri.org; from 1926-1949, interpolated for each year using the 1925 estimate from McEvedy and Jones and the 1950 WRI estimate assuming exponential population growth. For 2004, I excluded the deaths due to the Boxing Day Tsunami disaster (which, according to EM-DATA killed 226,435 people). Data on deaths, in particular, are approximate and, probably, more prone to error as we go further into the past.