Earth and Water

Graphs of The Pause are valuable as a means of confounding Global Warming Enthusiasts by showing how little temperatures have increased in the past couple of decades, but there are many other gems in monthly Temperature of the Lower Troposphere (TLT) anomalies. In this post I take a different look at monthly data using UAH v.6.0 for various regions.
Click on images to expand them.
First, here is the complete TLT record for the globe from December 1978 to December 2015.

Globe all
A trend of +1.14C/ 100 years, although anomalies have definitely flattened (the Pause) since about 2002.
But here are the Land and Ocean data separately:

Global land

Global ocean

Due to the oceans’ greater thermal inertia, it is to be expected that land areas would warm faster than oceans in any warming scenario no matter its cause. The Pause remains as well.
Notice the arrow at the beginning of 1998, marking the spike of the 1997-98 El Nino.  Note that the Land data after this are flatter and slightly stepped up from the data before this. The Ocean data give no hint of this, where since June 1994 the trend has been less than +0.1C (+/- 0.1C) per 100 years. Globally, Oceans have contributed nothing to global warming for well over half the satellite era.
Is this step change evident in other Land regions?

Northern Hemisphere:

NH land
Southern Hemisphere:

SH land
There is no sign of a step change in these data.   The step change is limited to the Northern Hemisphere.

Trop land

There is a flattening in the Land data from about 2001-2002, but no apparent step change.  The step change is limited to the Northern Hemisphere, but outside the Tropics.

North Polar:

NP land
No step change in 1998, although temperatures began changing in the mid-1990s.
Therefore, the 1998 step change must be in the data from the Northern Extra-Tropics (20-90 North), and specifically from 20N to 60N.

Nextr land

There’s the culprit. There is a clear discontinuity at the beginning of 1998. This graph shows it more clearly, with plots of data before and after this step change.

Nextr 2 parts
The whole record for the Northern Extra Tropics Land shows a linear trend of +2.04 degrees Celsius per 100 years. But the trend for the first half of the record (229 out of 445 months) is only +0.6C/ 100 years, and for the past 18 years only +0.36C/ 100 years. The rapid rate of warming overall is largely due to a step change in early 1998.
Here is the plot for the Northern Extra Tropics Ocean data:

Nextr ocean
The step change is not clearly defined, but the trend change is dramatic: +0.84C/ 100 years to zero.
This graph shows Land and Ocean data on the one plot, together with mean temperatures for both of them before and after the step change. The scale has been changed to highlight the differences.

Nextra land and ocean
Land data steps up by +0.48C and Ocean data by +0.26C.
What have we learnt?
The different behaviours of Land and Ocean data suggest that global warming trends are difficult to interpret.
Land TLT is warming faster than Ocean TLT.
North of 20S, Tropical and Northern Extra Tropical Land TLT data show warming above +2C, nearly 50% more than Southern Extra Tropical Land. (There is not much land compared with water south of 20S).
Global warming, by whatever cause, is dominated by Land warming, and by the Northern Hemisphere (which has most of the land area).
Warming in the Northern Hemisphere is dominated by a step change of nearly +0.5C at the beginning of 1998 in data for the Lower Troposphere over Land areas between 20N and 60N- by far the largest Land area on the planet, and the most heavily populated and industrialised region.
Significantly, this warming step change also contributed to the Pause, as temperatures since then have flattened.
We live in interesting times. Indeed, we are on the cusp of finding, over the next 4 to 5 years, whether the Pause has been a temporary slowdown as temperatures step up to a higher level, a longer period of levelling temperatures, or a brief plateau before a cooling phase.

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6 Responses to “Earth and Water”

  1. Neville Says:

    Interesting work Ken. But what would the result be if we had 2 big volcanic events after 1997 as we’ve seen in the first part of the UAH record? Surely that would have reduced the trend even more and perhaps resulted in some cooling over the last 18+ years?
    It is the one natural difference we’ve seen before 1997 that doesn’t even up after 1997. And as far as I know humans do not cause volcanic events.

    • kenskingdom Says:

      It could be argued that the step change is temperature catching up after the early 1990s slow down, but this should have occurred in the tropical area too. It is apparent that natural variation overwhelms greenhouse warming.

  2. robinedwards36 Says:

    I would really like to get the identical data that you used for the plots. Your analyses/conclusions seem to me to be very sound. I would tackle the data somewhat differently, but would arrive at something similar to your conclusions I believe. I am a fervent not-believer in fitting linear models to data that are clearly (generally graphically) not linear. This is the gross mistake that climatologists seem to make with seldom any dissent from statisticians. I guess that the latter can hardly believe what they are reading/seeing.

    Do you have the data in some sort of text format, or have you a direct link, which would save me a lot of searching?

  3. Neville Says:

    Another top post from Lord Monckton showing that the modelling of temps from 1990 to present are way ahead of actual observations. His circular graphs make it easier to understand. Needless to say that the Watts et al surface study’s clean sites and satellites are showing similar lowest trends. Although Watts et al is slightly lower .

  4. robinedwards36 Says:

    Many thanks for the link. I’ve collected the data and hope to find some time to look at soon. However, a considerable and unexpected family problem occurred yesterday which will take up an amount of time and effort.

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