It’s that time of year for breathless reports about planetary heating. Multilateral institutions, including the United Nations, recently made worldwide headlines, proclaiming 2023 as the hottest year in history.
The increase in average temperature, versus the longer-term average from 1850 to 1900, was a rise of 1.48 degrees Celsius. However, with the considerable difficulty of having truly comparable sets of measurements (from different sites in different years), one should treat such claims carefully. Interested parties use them to promote ‘solutions’ that could do more harm than good. It is notable that this new ‘high’ temperature was only 0.17 degree Celsius higher than in 2016.
NASA notes five factors explaining higher temperatures. Only one is the ‘usual suspect,’ greenhouse gases (mainly carbon dioxide, ‘CO2’). The other four are: the El Niño Southern Oscillation, ‘ENSO’, cycle; aerosol levels (such as smoke, dust and air pollution); volcanic eruptions; and general ocean temperature level and trends. NASA says the first and last of these affect current overall temperature.
The world has been in what meteorologists call an El Niño phase, which brings much higher temperatures to most of the world when it prevails. The oceans have also been gradually warming for decades, with occasional pauses, as in the period 1998-2013.
There are other major reasons to make an observer skeptical of extreme claims. The first is that this is a ‘history’ that is relatively short; i.e., the past 150 years (or even, in practice, much less). A second reason is that wide-scale, reliable global satellite temperature measurement has only been possible since the 1970’s. Before that, temperature monitoring was not systematic.
Until the 1880’s, temperature recordings were mostly in either North America or Europe, and hence show major data biases. Another crucial bias was that many weather stations are in or close to cities, which grew and warmed as they burned more coal (and, later on, more oil and natural gas), causing the heat island effect. The cities, growing gently warmer, also grew toward the weather stations, usually located on the outskirts of cities, especially the stations at airports.
For example, there are two weather stations in Winnipeg – one at the wind-swept airport and the other in the heart of downtown at the Forks. An analysis back in 2007 showed the temperature difference between the two locations to be 1.57 degrees warmer at the Forks. So closing or ignoring the airport temperature measurement location would “on paper” show warming in Winnipeg. It will be the same with most major Canadian airports.
Another valid way to challenge an assertion that 2023 was history’s hottest year, is to examine other time periods to see if one was hotter. The most well known such period came in the 1930’s, which was hotter and drier than the decades before or after. High temperatures set many new records that remain unbroken. The 1970’s were cool, despite rising CO2 emissions.
The Medieval Warm Period, approximately AD 750-1350, was much warmer than today. Farming was commonplace in Greenland, and vineyards grew in Britain. Industrialization began in the 1750’s, so, increased levels of greenhouse gas emissions could not and did not cause ancient warming. Nor did lower CO2 emissions cause the subsequent cooling of the Earth’s atmosphere, which culminated in what is now called the Little Ice Age, AD 1350-1850, from which we are still emerging.
According to interested parties the past year may have set records, but there is no evidence that it was the ‘hottest’.
Its summer time. Enjoy the hot weather. Ignore the climate doomsters.
Ian Madsen is the Senior Policy Analyst at the Frontier Centre for Public Policy
