over 120 years yields the strongest realism for grasping earth's trend:
a natural sine curve.
The graph above, a plot of TMAX records collected by NOAA, reveals Daily Maximum Temperature modulating in a sine curve through 4.20 degrees Fahrenheit, 63.30 - 67.50 [through 2.38 degrees Celsius 17.39 - 19.77]. We are fortunate to have this expansive sampling that spans two full warm/cool cycles. No other precision sampling equals it.
The chart is compiled from 49,868,490 daily readings of Daily Maximum Temperature (TMAX) from all US reporting stations. With a sample-size of fifty million data points, and bias corrections from NOAA respected, the claim "temperature is following a normal sine wave" can be stated with high confidence.
After the blistering hot decades of the 1930s and 1940s, the steady drop headed into the 1970s set off alarms in climate science that earth was in danger of a new ice age. Then, with the rise of a new cycle in the period 1980s and 1990s, the alarm switched to danger of catastrophic warming and ocean rise.
Now, the trend is down again, although no one seems very alarmed about that ... yet. This is the Holocene, with a long slow drift down until the start of a new glaciation -- which could arrive tomorrow, or in 5,000 years.
63.31 F, second lowest in history.
Other forms of measurement are valuable, such as with satellites and ocean probes, but they only plot recent data. Anomaly graphs of short slices of those recordings – especially if they contradict the 120-year measured record – are subject to skewed interpretation. Tree ring, ice core, and other proxies cannot resolve detail of this precision.
fifty million direct observations over 120 years is the truth.
in the dataset of USA direct measurement.
+2.53 Dropping 1999-2020
+2.76 Dropping 2017-2020
Temp goes up and down in a sine curve, nature's normal rhythm.
The cycle over the last 60 years is lower than the 60 years prior. Natural easing of Holocene warmth? Impetus after 2019 heading into a meta-cycle like the Little Ice Age? A cycle within a cycle within a cycle? Stay tuned ...