Ian, as you said you have worked with the climate data, do you find fault with the article in Pete's post no. 172. It seems that the 30 year cycle is well correlated with the ocean temps and glacier expansion and contraction.
Again, all climatologists agree that the earth goes through warming and cooling cycles.
Two of the things that bother me with Easterbrook's conclusions: 1) he downplays the
steady increase in temp since 1500, even taking into account the Little Ice Age, and
provides no explanation, and 2) he doesn't even mention the significant change in
the rate of rise since the Industrial Revolution, which is where the rise in CO2 comes
from. If he had addressed these issues in some way, and provided some sort of
explanation as to why the cooling trends have not dramatically "normalized" the
temperatures long term, then I would say he has a rock solid argument. By not
doing so, it clouds his conclusions somewhat. Then it makes you ask why he does
not talk about those issues.
There are others who question Easterbrook's conclusions on other bases - that his
assumption of increased Solar Irradiance in the first half of the 20th century didn't
happen based upon other measurements, so it cannot directly explain the warming
trend measured since then. That's not to say there isn't some correlation between
the Sun and our climate, but it might not be as direct as Easterbrook would like.
Now, I am not a climatologist by trade nor by education, I just worked with the
ocean temperature numbers and wrote programs to generate graphs and plots,
so there is much about all of the theories that I do not fully understand. However,
looking at the numbers (ocean temp, solar irradiance, etc.), the fact that a general
warming trend has existed since the 1500s, and has gotten sharper since the late
1800s, points to something disrupting the natural cycles.
Ian