claim: Actual reconstructions "diverge" from the instrumental series in the last part of 20th century.
evidence: In the North Atlantic, sediments accumulated since the end of the last ice age, nearly 12,000 years ago, show regular increases in the amount of coarse sediment grains deposited from icebergs melting in the now open ocean, indicating a series of 1–2 °C (2–4 °F) cooling events recurring every 1,500 years or so.