Greg Tomlinson and I have been discussing global warming in a series of comments and replies to a blog post of mine from April 2017. Readers can review this discussion here1, here2, here3, here4, and here5. This back and forth primarily deals with the evidence that Earth’s average surface temperature has been increasing for many decades as the result of humans burning fossil fuels. As our discussion focuses, for the most part, on the details of the global average surface temperature record derived from thermometer measurement records, readers might get the impression that this is the single key data record that shows the Earth’s warming and that it is a close question as to whether the globe is warming or not. In fact, the results of analyzing temperature records are fully consistent with many other lines of evidence that the globe is warming. These other lines of evidence do not involve the detailed analysis of world-wide temperature records. I’ll describe a few of these, but there are, literally, dozens of such striking demonstrations that the globe is warming.
These examples are point measurements that suggest but do not tell us about global climate. Therefore, the professional researchers go through the immense trouble to produce a global average surface temperature. Even that is not the only global climate measure they produce. Indeed, the temperature record at each weather station is a point measurement.
Here’s a proxy temperature record from Japan that goes back to 800 AD. The graph is from an article in the Economist, but the data points are from a publication by a Japanese researcher. He and his colleagues investigated records of cherry blossom viewing going back 1200 years, nearly to the beginning of Japanese civilization. The vertical axis shows dates in April, except for a few early in May or late in March. The Economist writers have graphed the Japanese researchers’ data and averaged it. The date at which the blossoms reach their peak is a proxy for the temperature: earlier warm temperatures produce earlier peak blossoms. Dots lower on the chart are earlier in the season and reflect warmer springs. Of course, over the centuries there are wide variations. To my eyes, the peak blossom dates have moved earlier by about two weeks since the early or mid-1800s. What do your eyes see? Climate fluctuations known to scholars as the medieval warm period, around 1000 to 1200 AD or the little ice age around 1400 are European climate phenomena, not world-wide ones. The movement of the most recent 100 years or so is larger than any of the earlier fluctuations, in 12 centuries, and shows no sign of moderating.
Cherry blossoms tell us about the arrival of spring warmth. It’s getting warmer earlier. What about the arrival of fall’s chills? They are arriving later.
Gingko trees lose most of their leaves shortly after, indeed often during the night of, the first autumn freeze. People have been recording the date on which a gingko tree at the University of New Hampshire drops its leaves since the 1970s. Evidently the biology student amuse themselves with a betting pool. The school in Durham is close to New Hampshire’s short Atlantic Ocean coast. Here’s the data. Julian day, the vertical axis, is the day of the year beginning with January 1 as Julian Day 1. This year’s leaf fall was the second latest in this record. It looks to my eyes as if the trend line is now about 10 days later than it was in the late 1970s.
This interesting chart is from a New York Times article: How Much Warmer Was Your City?
You enter your city in the window. They have data from many cities around the world. I’ve just put in the Tampa data because I live and teach here.
The horizontal axis shows the days of the year, grouped by month. The vertical axis shows temperatures for each day in Fahrenheit degrees. For each day, the black vertical bar shows the high and low temperature for that day. The dark gray shows the normal temperatures for that day, and the lighter gray shows the record high and the record low for that day. By the way, you can see that last December was unusually warm in Tampa. You can see the general sweep of the seasons from temperate to steamy hot to temperate.
If the climate in Tampa were stable, you’d expect to see a few record highs and a few record lows throughout the year. The records could, just randomly, come at any time. So, an unusually hot winter day or an unusually cold summer day. Perhaps, you’d see 4 record lows and 6 record highs one year, then 5 record lows and 5 record highs the next, and so on. But in 2016 Tampa had 15 record highs and 0 record lows! The small vertical arrows mark the records. This suggests that the climate has warmed relative to the long term historical climate.
I encourage you to visit this site and enter your own city.
Alaskan rivers freeze during the long cold winters, and the ice breaks apart in the spring as weather warms. People have been recording, and betting upon, the breakup date for more than a hundred years. Here’s the data for two rivers in Alaska: Ice Breakup on Two Alaskan Rivers.
This is from the still worthwhile EPA site: Climate Change Indicators, which has many similar records from distinctive sources, all of which are broadly consistent with a warming climate.
Notice that in the graph, upward is earlier in the year, which is also presumed to mean warmer earlier. To my eyes, it looks as if the breakup is about 0 days later than it was a hundred years ago.
The figure figure shows the date each year when ice breaks up at two locations: the town of Nenana on the Tanana River and Dawson City on the Yukon River.
Here is data about arctic sea ice coverage from the excellent National Snow and Ice Data Center: Arctic and Antarctic Sea Ice News.
This data arises from systematic recording from satellites in polar orbits that have been collecting data since the 1970s. You can see the line for the 1981-2010 median. The two shades of gray show plus and minus 25% and plus and minus 45%. The year 2012 was the record low, but you can see that recent years have all been outside the usual range. Indeed, in recent years cargo ships, with strengthened hulls but no accompanying ice breakers, have traversed the famous Northwest Passage over the top of Canada, and over the tip of Russian and Siberia. These are much shorter routes Asia to Europe and the eastern US.
There is much more useful material at this site, about Antarctic sea ice, for example.
Figure 2a. The graph above shows Arctic sea ice extent as of November 2, 2017 along with daily ice extent data for five previous years. 2017 is shown in blue, 2016 in green, 2015 in orange, 2014 in brown, 2013 in purple, and 2012 in dotted brown. The 1981 to 2010 median is in dark gray. The gray areas around the median line show the interquartile and interdecile ranges of the data. Sea Ice Index data.
Credit: National Snow and Ice Data Center