Every winter in North America, when there is a period of above seasonal temperatures, conversation turns to a familiar subject, the weather. It generally starts with comments like the warmer temperatures are ‘a terrible consequence of global warming’ and then ‘every year the global temperature gets warmer and warmer’. We hear these comments on the street, in the gym and even on news and weather broadcasts. These have become fashionable sound bites and conversation starters. And sadly, they have also become a rally cry to solicit support for political dogma.
In this blog post, I will explain why I believe these weather statements are false.
Over the past two years in North America our winters have been profoundly affected by the El Niño Southern Oscillation System, referred to as ENSO in climatic circles. The El Niño phenomenon is associated with a band of warm ocean water that develops in the central equatorial Pacific. It produces a very mild winter in North America and very wet conditions in South America. This warming also causes a shift in the atmospheric circulation with rainfall becoming reduced over Indonesia and Australia, while rainfall and tropical cyclone formation increases over the tropical Pacific Ocean.
El Niño is a cyclical, short lived event lasting from between 1 to 3 years. It is a coupled phenomenon whose subsequent counterpart is La Nina, resulting in cooler than average sea surface temperatures in the central Pacific Ocean. La Nina immediately follows, and has the opposite effect of El Niño: a colder winter in N America, drought in S America and heavy rains in Southeast Asia.
There have been at least 30 El Niño events since 1900 (Figure 1), with the 1982-83, 1997–98 and 2016-17 events among the strongest on record. Other El Niño events have been recorded in 1790–93, 1828, 1876–78, and 1891. It is also believed that El Niño affected the Inca Empire, who sacrificed humans in order to try to prevent the rains. Scientists have also found that chemical signatures in 13,000 year old coral samples indicate warmer sea surface temperatures and increased rainfall caused by El Niño. In other words, we have evidence of El Niño going back tens of thousands of years. This not a man-made phenomenon.
In the last 30 years, the eastern hemisphere has been significantly effected by two El Niño events, in 1998 and in 2016. Both were exceptionally strong and both winters in North America were extremely mild.
Many attributed the effects of these two Los Niños to global warming. However, there are fundamental differences between the El Niño and Global Warming: the former is a short duration event, coupled by a subsequent cooling event (i.e. La Niña) and a return to seasonal temperature; Global Warming from an activist perspective, is the continued warming of the planet.
In order to establish a global warming trend, one needs to look beyond cyclical weather patterns and see what’s happening between El Niño events.
First, let’s look at the temperature data measured from satellites. This is considered more reliable than land based temperature data, but unfortunately we only have 40 years of it. However, it does allow us to examine in detail, with data confidence, a critical period from 1998-present.
Since 1979, the National Oceanic and Atmospheric Administration (NOAA) have been recording global temperature from satellites and this is presented in Figure 2.
If you look closely at the last 20 years, from the large El Niño of 1998 to the very large 2016 El Niño event, the global temperatures have been essentially flat. Note how this differs to the rate of warming between 1979 and 1998. A change in warming rate has occurred.
To look back beyond 1979, we need to look at the less reliable, land based thermometers. In Figure 3 below, the fossil fuel era, which activists believe created global warming, commenced after WWII. From 1975 to 1998, the planet was warming at a rate of ~0.2C°/decade. NASA believes that two-thirds of global warming has occurred since 1975. And this period, between 1979 and 1998, has highest rate of warming in the last 100 years!
However, what happens in the subsequent 20 years is fundamental to the global warming discussion. Compare the rate from 1975-1998 to the period from 1998-2016. In the past 20 years, the planet’s temperature has not continued to rise, in fact it has dramatically slowed. And the same decrease in warming is observed in the satellite data in Figure 2. Both sets of temperature data tell the same story.
Why has the planet stopped warming? And why has this happened while the supposed culprit, CO2 from fossil fuels, has continued to rise?
In Figure 3, the surface temperature data also begs another question. Why is there a temperature increase from 1900-1950, a period when fossil fuel consumption was only 10-15% of what it is today? ( Source: BP World Energy Consumption)
The answer: CO2 does not warm the planet. If that’s true, you ask, what is causing the warming and cooling of our planet?
There is still much we don’t fully understand about our climatic processes. One possibility as to why there is a stop or pause in global warming in the last 20 years, is that we are entering a period of limited solar activity, the earth has already started to cool, and the interglacial warm period that we have enjoyed for the past 120 years is (sadly) coming to an end ( See: The Earth’s Upcoming Ice Age blog post).
However, others have suggested climate change is driven by other often interrelated factors like changes to the temperature of the Pacific Ocean, plate tectonic and volcanism, solar activity, solar dust, Milankovitch cycles, and water vapor (i.e. cloud cover). More integrated science is required to understand the complex climatic process.
Whatever the cause, the Earth’s rate of warming has dramatically slowed, paused or stopped over the past 20 years. Previous predictive climatic models generated in the past 10 years have been wrong and significantly overestimated the amount of warming that should have occurred. This warming hasn’t happened.
So next time someone is making fashionable climate change small talk and says ‘Man is causing our planet to get warmer each year’ you could ask, ‘Over the last 20 years, why has the rate of global temperature increase not continued?’
However, a word of caution, many will not like this. It will be a challenge to political beliefs and a moral high ground that will be too much to accept.
Unlike political dogma, science absolutely relies on asking unpopular, difficult questions. Earth scientists must ask these questions. It is a fundamental part of the iterative process that leads to higher understanding and ultimately discovery.
And science should not be socially or politically muzzled. If we only allow popular, fashionable and politically correct views into the scientific arenas, we move backwards into the dark ages of science.
Our environment is fundamentally important to our well-being. And if we are to care for it properly, with proper scientific understanding, we must continue to ask difficult questions and find groundbreaking answers.