“The climate has always changed.”
You often hear that statement when the possibility of manmade (or anthropogenic) climate change is discussed.
It is a true statement, of course. The earth’s climate has been in a constant state of flux due to a variety of natural factors, such as changes in the earth’s orbit, variable output from the sun and fluctuations in the concentration of greenhouse gases in the atmosphere.
Of all the factors listed above, only the changes in greenhouse gas concentrations can account for the current and ongoing rapid changes in climate, with carbon dioxide from the burning of fossil fuels being the most important of those gases.
In most cases, those previous changes in climate occurred over long periods, on the order of thousands to millions of years. The slower rate of change allowed the ecosystem to adjust to those new levels.
When climate changes abruptly, however, the results can be highly disruptive, and even destructive, to life.
And therein lies the reason for concern over the relatively rapid changes in climate occurring today.
The warming effect of carbon dioxide and other greenhouse gases is well understood, a cornerstone of the basic physics of radiative transfer.
Without their heat-trapping effect, the earth would be a frozen, lifeless ball of ice with an average temperature of around 0Â°F.
When carbon dioxide concentrations decrease, like during the cyclical ice ages of the past million years, the earth becomes much colder.
When they increase, such as during the interglacial periods separating those ice ages, temperatures increase.
During the current interglacial period, carbon dioxide concentrations have remained stable around 280 parts per million (ppm), providing a stable, reliable climate for our civilization to expand and thrive.
An upward trend that began over a century ago continues, and today’s mark now stands at more than 400 ppm.
The earth’s average annual surface air temperature has increased by about 1.6Â°F over the last 150 years.
That might not seem significant, but keep in mind that is an average over the entire globe. Within that number exists much larger changes, and indeed, much smaller changes over different areas.
Near the Arctic Circle, for example, the temperature rise has been much more significant – at a rate nearly twice the global average, and the extremes and impacts reflect that.
In February, temperatures soared to more than 50Â°F above normal in the Arctic. In 2016, the warmest year on record since modern records began in 1880, the global temperature anomaly was about 1.8Â°F above normal. The Arctic was more than 3.5Â°F above normal that year, however.
Paleoclimate data – tree ring studies, ice cores and so on – indicate that the average temperatures in the last few decades are unusually warm compared to the last 1,700 to 2,000 years. In fact, 17 of the 18 warmest years on record have occurred since 2000, and the six warmest since 2010.
Long-term temperature observations are the easiest and most consistent piece of evidence pointing toward a warming world, but Mother Nature has her own natural thermometers.
According to the best and most recent scientific studies available today, there are more than 25,000 independent lines of physical and biological evidence of a warming world, including increasing ocean heat content, ocean acidification, decreasing ice sheets, snow cover and glaciers, increasing atmospheric humidity, species migrating poleward and upward, and spring arriving earlier in association with shorter winters.
Many people in the industrialized world probably don’t recognize climate change on a day-to-day basis.
They’ve become “adjusted” to the differences in the weather patterns that make up the larger climate picture.
They do notice weather extremes, however, and those extremes are likely to be their first introduction to climate change.
Heat waves, the intensification of drought, fewer record cold days, sea level rise and the increase in both intensity and frequency of heavy precipitation events (and the associated flooding) are all examples of extreme weather that accompany global climate change.
The ability to adapt to those extremes will obviously be difficult, but certainly much easier for the more affluent countries on the globe. The impacts are expected to put the poorest at most risk.
As noted by the National Academies, “There will be winners and losers from the impacts of climate change, even within a single region, but globally the losses are expected to far outweigh the benefits.”
Gary McManus is a climatologist with master of science and bachelor of science degrees in meteorology from the University of Oklahoma.
Editor’s note: This article is part of a series focused on creation care for Earth Day 2018. The previous articles in the series are:
How Martin Luther King’s Death Birthed Environmental Justice by Aaron D. Weaver
How Churches Can Turn Around Our Environmental Woes by Chuck Summers
Why Our Worship Must Focus More on Creation Care by Helle Liht
Pastors Share How Their Churches Support Creation Care by Zach Dawes