Climate Oscillations 3: Northern Hemisphere Sea Ice Area

By Andy May

Northern Hemisphere sea ice area is an important climatic indicator because it determines how much of the Arctic Ocean and surrounding seas are open to the atmosphere. Ice is a good insulator and traps heat in the water below it (Peixoto & Oort, 1992, p. 361). Ice is also a good reflector of sunlight (high albedo), whereas water is a good absorber (low albedo). While we have no accurate data on Northern Hemisphere sea ice area (called NH_ice here) before 1978, the first year of good satellite data, it does appear to follow the global 60-70-year global climate oscillation (Wyatt, 2020). This may be because the closely related AMO affects the sea ice area as it warms and cools, of course the reverse could also be true.

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Climate Oscillations 2: The Western Hemisphere Warm Pool (WHWP)

By Andy May

As seen in the first post of this series the AMO (Atlantic Multidecadal Oscillation) and the WHWP (Western Hemisphere Warm Pool) area are the two climate oscillations that explain most of the variability (64%) in the HadCRUT5 global mean surface temperature reconstruction (GMST) since 1950. Adding the Southern Annular Mode (SAM) explains 77% of HadCRUT5 variability.

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Climate Oscillations 1: The Regression

By Andy May

Introduction to the “Climate Oscillations” series

My last two posts, Musings on the AMO and The Bray Solar Cycle and AMO were fun to research and write, and they helped show that solar variations and cycles do have an impact on climate change regardless of what the IPCC says in AR6 WGI and their other reports.

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The Bray Solar Cycle and AMO

By Andy May

My last post on the AMO and HadCRUT5 generated some interest and some criticism. As I explained, there are two common methods of computing the AMO index. One is to fit a least squares line to the AMO SSTs (sea surface temperatures in the North Atlantic) and use the line to detrend the AMO, creating an index. This was the original methodology as described by Enfield, et al. and Gray, et al. It is the method I prefer because it makes no assumptions about the origin of the increasing SSTs in the North Atlantic.

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Musings on the AMO

By Andy May

We hear a lot about the AMO, or the Atlantic Multidecadal Oscillation. How much does it influence the global mean surface temperature or GMST? Exactly what is the AMO? These are the issues we will discuss. First let’s look at various definitions of the AMO.

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Energy Consumption in 2024 and the Spanish Power Failure

What does the April 2025 Spanish power failure tell us about how we compare solar and wind to stable fossil fuel and nuclear power generation?

By Andy May

Global energy demand and consumption rose 2.2% in 2024 to a record high according to the 2025 IEA Global Energy Review released in March 2025. Growth in fossil fuel consumption accounted for 54% of the growing demand and growth in renewables and nuclear power accounted for the remainder. Most of the consumption growth was in emerging nations. The total energy supply for 2022-2024 is given in Table 1.

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The Weather and Climate of World War II

By Andy May

This post has been translated into German for those who prefer it here.

In my last post I discussed the evolution from the ICOADS raw sea surface temperature (SST) data to the final ERSST and HadSST SST anomalies. These anomalies are compared in figure 1. The ICOADS anomalies are generated by subtracting the 1961-1990 mean value from all the final raw simple yearly means. This was done last after the simple global mean SST had been computed for all years.

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What is the Global Average SST?

By Andy May

This post can be read in German here.

The global average SST (Sea Surface Temperature) is a very important component of the global average surface temperature for the simple reason that the global ocean covers almost 71% of Earth’s surface. So, we downloaded the gridded SST data from 1850 through 2024 from the Hadley Centre (HadSST v4.1), NOAA (ERSST v5), and NOAA’s SST data repository (ICOADS v3) and then plotted the data in figure 1.

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Plate Tectonics and Climate during the Cenozoic

By Andy May

This post has been translated to German by Christian Freuer here.

In this post I examine the proxies used to compare CO2 to temperature from 66 million years ago (Ma) until today and comment on the quality of the comparison. In addition, we look at the Cenozoic plate tectonic events that affected global climate. Figure 1 compares Westerhold et al.’s deep-sea d18O (the Oxygen-18 isotope anomaly, a temperature proxy) to the d13C (the Carbon-13 isotope anomaly), both measurements are from the same fossils, so they can be directly compared. One of the problems with many temperature/CO2 plots is often they are from different sources and locations and due to dating errors and differing temporal resolutions, they are not directly comparable. While d13C is not a direct CO2 estimate, it is related to the CO2 concentration in the deep ocean. Atmospheric and ocean CO2 concentration estimates are compared to d13C in figure 2.

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The Earth without Greenhouse Gases

By Andy May

The overall greenhouse effect (GHE) is often defined as the difference between Earth’s average global temperature without greenhouse gases (GHGs) and with them. Greenhouse gases are all the gases that absorb some portion of the thermal energy emitted by Earth’s surface. The most important of these gases is water vapor, but there are minor GHGs like CO2, ozone, and methane.

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