The IPCC report Global Warming of 1.5°C, and the Fourth National Climate Assessment were not the only climate related reports to be published in the second half of 2018. The American Meteorological Society also published its annual report on the climate, State of the Climate in 2017. Rather than a document assessing the effects of climate change, this documents presents a comprehensive picture of what the climate was like in 2017.
Figure 1 shows in a single graphic the major climate variables that are discussed in the report. I will discuss each very briefly in order, going down each column before moving to the next column. I’ve made the chart to open in a separate browser tab, and you should be able to refer back and forth between my comments and the charts. In the charts, some of the data is shown as anomalies rather than as raw values, and in those cases, the reference period is given in the chart.
Charts (a) and (b) show the level of polar ozone, the 1st in March, the 2nd in October. This ozone is high-altitude ozone, and it is essential for blocking ultraviolet rays, too much of which are harmful. These charts concern the famous ozone hole of the 1980s. In general, the level in March bottomed in the 1980s, partially rebounded, but has again been trending downward. In October, the level bottomed in the 1980s and has been largely moving sideways since then.
Chart (c) shows the average surface temperature in the arctic. It has obviously been warming, some 3°C since the 1950s.
Chart (d) shows the average surface temperature of the whole earth. It has been warming, but not as much as the arctic. The recent several years show a steep spike upward.
Chart (e) shows temperature in the lower troposphere. This is the lowest layer of the earth’s atmosphere, and it is where almost all life occurs, as well as almost all weather. It has been warming, and you can see the same spike in recent years.
Chart (f) shows the temperature in the lower stratosphere. This is the next higher layer of the atmosphere. Near the equator it begins some 66,000 feet up, while at the poles it is lower, some 23,000 feet up. The temperature here has been cooling. I have seen some arguments that the cooling in the stratosphere compensates for the heat in the troposphere. This is like saying that cool weather in San Francisco means people can’t be dying from a heat wave in Chicago. Sorry, but it doesn’t mean any such thing.
Chart (g) plots the number of warm days (solid line) and cool nights (dotted line). Warm days have been increasing, and cool nights have been decreasing.
Chart (h) shows the area covered by arctic sea ice. The maximum is the solid line, the minimum the dotted line. Both have been decreasing, the minimum more severely.
Chart (i) shows antarctic sea ice. The variability between years has grown significantly, and the general trend appears to be increasing.
Chart (j) shows a measure of the amount of water locked-up as ice in all of the world’s glaciers. It has been declining at a significant rate. It will have implications for anyone and anything dependent on glaciers and/or glacial melt for water.
Chart (l) shows the amount of water vapor in the lower stratosphere. It is quite variable, but the trend appears to be toward slightly higher amounts of water vapor.
Chart (m) shows the level of cloudiness across the planet. There are several data sets. The trend appears to be towards convergence, with a slightly downward slope for at least some of the data sets.
Chart (n) shows the amount of water vapor in the entire atmosphere, top to bottom, over land. It has been increasing.
Chart (o) shows the amount of water vapor in the entire atmosphere, top to bottom, over the ocean. It, too, has been increasing.
Chart (p) shows the specific humidity in the upper troposphere. It appears to be declining slightly.
Chart (q) shows the specific humidity over land. It has been increasing. Specific humidity is not the humidity statistic we are used to, that is relative humidity (see below). The specific humidity is a measure of the mass of water vapor in an air sample compared to the mass of the other air in the sample.
Chart (r) shows the specific humidity over the ocean. It, too has been increasing.
Chart (s) shows relative humidity over the land. It has been decreasing. Relative humidity is a measure of the amount of water a sample of air is holding, compared to the maximum it could hold. Air’s ability to hold water increases with temperature, so it is possible for relative humidity to decrease, even while specific humidity increases, if the temperature rises.
Chart (t) Shows relative humidity over the ocean. It has been mostly moving sideways, but perhaps decreasing slightly.
Chart (u) shows the amount of precipitation over land. It moved mostly sideways until the 1980s, at which point it appears to have increased. The recent years have seen a significant spike upward.
Chart (v) shows the Southern Oscillation Index. This is a measure comparing air pressure in the western and eastern South Pacific. It tracks the El Niño phenomenon, with negative values indicating an El Niño, and positive values indicating a La Niña. I see no obvious trend in the data.
Chart shows the amount of heat the ocean is holding. The amount of heat is not the same as the temperature: a 100° pot of water holds much more heat than a 100° pot of air, though both are the same size. The heat content of the oceans has bee increasing.
Chart (x) shows a measure of sea level. It has been rising. The scale is in millimeters, so the chart shows about a 6-inch rise.
Chart (y) shows the tropospheric ozone level in the tropics. It has been increasing. This is not the same as arctic ozone levels, which are measured in the stratosphere, where they help to block ultraviolet light from striking the earth. This is ground level ozone, a harmful pollutant. It is the ozone I track when I report on the Air Quality Index.
Chart (z) shows a measure of the speed of the wind in the troposphere. It has been increasing slightly.
Chart (aa) shows a measure of the speed of the wind over land. It has been decreasing.
Chart (ab) shows a measure of the speed of the wind over the ocean. It has been increasing.
Chart (ac) shows the amount of biomass being burned each year. It has been deecreasing.
Chart (ad) shows a measure of soil moisture across the earth. It has been moving sideways, a surprise to me, as I would have expected increased temperatures to dry the soil.
Chart (ae) shows terrestrial water storage. Though the data series is short, it appears to be declining. This variable concerns fresh water, and reflects ice sheets, glaciers, and lakes. Its decline is a matter of concern for all people, animals, and plants that depend on stored water.
Chart (af) shows global FAPAR. FAPAR is the amount of solar radiation available for absorption by plants during photosynthesis that actually gets absorbed. Though the data series is short, it was declining, but in recent years it has increased.
Chart (ag) shows the albedo of the land surface. Though the data series is short, it appears to be decreasing. Albedo is the reflectivity of the earth. High albedo means most of the light is reflected. Low albedo means most of the light is absorbed, causing the surface to warm. Black paint has a low albedo, white paint has a high albedo.
Blunden, J., D. S. Arndt, and G. Hartfield , Eds., 2018: State of the Climate in 2017. Bull. Amer. Meteor. Soc., 99 (8), Si–S332, doi:10.1175/2018BAMSStateoftheClimate.1.