David said:
"Paul, do you have a way of quantifying the contributions of tidal vs. greenhouse effects to global warming?"


The tidal contribution balances to zero based on theory.

There is an interesting direct correlation between the earth's length-of-day (LOD) changes and tidal cycles. This is precise on all the well-known tidal cycles.

tides -> LOD (tidal forcing causes slight torques on the earth's rotation, causing a varying rotation rate)

tides -> ENSO (tidal forcing causes slight torques on the earth's angular momentum, sloshing the ocean)

However there is also a long-term quasi-periodic cycle from 40-60 years that the LOD and the climate seem to share, from this recent paper based on long term NASA JPL and Paris Observatory research (started in the late 1970s).

https://journals.ametsoc.org/ei/article/20/4/1/629 "Does an Intrinsic Source Generate a Shared Low-Frequency Signature in Earth’s Climate and Rotation Rate? "


![](https://ams.silverchair-cdn.com/ams/content_public/journal/ei/20/4/10.1175_ei-d-15-0014.1/3/m_ei-d-15-0014_1-f3.png?Expires=1594950914&Signature=p-jGoB5XieHYuDrOoLoLhSL8BYLd2KV3ibi8mMafDeYwKqlKtdNwV2NyopJXz~Tvqe98mCFOvrFpPj18GTj10l2R2ToaoBUstOIh9T1QjrjPG-vMj~nbbAd751I26dREWxitkwjAA3PR86vMomD6dIB~ijc7OHvxA~nmqDgrNzwEUsH8ZWPsQg0Gw7aZpEDl~xJYaztyG4wA4YIzXuukt8KElylOnuMnnGr6~Lbll8n5dfhm83-W6Pjiy8Ow0eeYFE~xTcObE~gjblyknoyifVJgcEobofMkTSTR-tQMseAJY~3wilnnXPyALbZKB5kkZK6cL9L8nMoXazYSs84Slg__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)

so there is this

unknown -> LOD

unknown -> PDO

unknown -> AMO

The distinction between ENSO and PDO/AMO is that PDO and AMO show some longer term variations, which are not difficult to reproduce based on the beat frequencies of closely spaced tidal periods.

![](https://imagizer.imageshack.com/img922/6507/VCzqqH.png)

(compress the horizontal so it looks the same scale as above)

![](https://imagizer.imageshack.com/img924/8793/tT9oJm.png)

which implies that

unknown = tides

This is intriguing but there's not a lot of data from which to draw conclusions from.