HadCrut is the black line in the graph above. For the ENSO five year running mean, dominantly El Niño periods are shown in red, and dominantly La Niña periods are shown in blue.
Everybody understands that temperatures warm up during El Niño, and they cool down during La Niña. Looking at the ENSO graph, it is painfully obvious what drove the post 1975 warming, and what caused the earlier cooling. When the Pacific Ocean is warm, the world is warm.
So why do climate scientists remain in denial?
Jackson noted that when researchers remove greenhouse gases from the climate models, leaving behind all the known natural sources of variability, the observed warming over the last century evaporates.
Are they really claiming that they don’t know about ENSO or the PDO?
HadCrut in black. PDO in red/blue.