When astronomical summer begins on Wednesday, a recurring image will pop up across the country and around the world. In addition, some landmarks around the United States will be illuminated with its colors — from Alabama to Massachusetts — to spread awareness of climate change.
With a pattern similar to a barcode, these stripes were created by Ed Hawkins, a climate scientist at the University of Reading in England. Originally, each stripe depicted the global average temperature each year since 1850 using data from the U.K. Meteorological Office. Each color of each stripe corresponds to a year when the temperature was above the long-term average (red) or below (blue).
In the past few years, several versions of the pattern have emerged. Data at national, state and local levels can be used to show how the temperature has changed at individual locations around the world — including in the oceans.
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With few exceptions, the stripes show the gradual transition from blue to red, illustrating the dramatic warming over the past few decades. And while any individual year may be warmer or cooler than average, the warming of the last 40 years dominates the signal.
After the scientific community looked for multiple reasons for the warming — from solar output to local land use — the overwhelming evidence showed that the warming comes from the burning of fossil fuels.
Burning coal, oil and natural gas releases carbon dioxide into the atmosphere. That gas, even in amounts that seem very small, helps keep the planet warmer. The impact is especially strong in areas that are cold to begin with and do not get a lot of sun in the winter — one of the reasons why the Arctic is warming about three times faster than the rest of the planet.
Evidence continues to mount. Global ocean temperatures had back-to-back record warm months in April and May. North and South America each just had their warmest May on record. The last seven years haven been the seven warmest in the 174-year global record. And 2023 is on pace to finish in the top five.
Since the late 19th century, the planet has warmed about 2 degrees Fahrenheit, and current global energy and emissions policies are on track for 5.5 degrees of warming by 2100. However, precisely how much additional warming will depend on how closely the actual emissions in the coming decades mirror those policies.
Every tenth of a degree matters in the long-term, as it raises the risk for longer and stronger heatwaves, more intense rainfall and more coastal flooding. Reliable agricultural zones will continue to shift, fishing areas will become less dependable as their populations relocate, and pollen seasons will become longer with less time of the year below freezing.
However, there are some encouraging signs. Coal, which is one of the dirtiest of the fossil fuels, is being phased out as the cost of natural gas has fallen. As a result, many states have seen their emissions take on a slow decline in the last 15 years.
Solar and wind energy is beginning to scale upward. China, India and the U.S. are all expected to triple their solar energy capacity over the next five years, and wind energy now generates about 10 percent of all utility-scale electricity generation in the United States.
But more work will need to be done; the concentration of carbon dioxide in the atmosphere has risen 33 percent since 1958, and it continues to climb. As long as that number continues to go up, expect the stripes to show up every year around this time, and probably even more so in the near future.
And those new stripes added to the image will be a deep red for years to come.
