July 2012 Nature Climate Change study says earth orbit variations have 4x more influence on climate than man, and past 2000 yrs. show cooling

7/8/12, "Orbital forcing of tree-ring data," Nature Climate Change study

"Solar insolation changes, resulting from long-term oscillations of orbital configurations¹, are an important driver of Holocene climate^{2, 3}. The forcing is substantial over the past 2,000 years, up to four times as large as the 1.6 W m⁻² net anthropogenic forcing since 1750 (ref. 4), but the trend varies considerably over time, space and with season⁵. Using numerous high-latitude proxy records, slow orbital changes have recently been shown⁶ to gradually force boreal summer temperature cooling over the common era. Here, we present new evidence based on maximum latewood density data from northern Scandinavia, indicating that this cooling trend was stronger (−0.31 °C per 1,000 years, ±0.03 °C) than previously reported, and demonstrate that

• this signature is missing in published tree-ring proxy records.

The long-term trend now revealed in maximum latewood density data is in line with coupled general circulation models^{7, 8} indicating albedo-driven feedback mechanisms and substantial summer cooling over the past two millennia in northern boreal and Arctic latitudes. These findings, together with the missing orbital signature in published dendrochronological records, suggest that large-scale near-surface air-temperature reconstructions^{9, 10, 11, 12, 13} relying on tree-ring data may underestimate pre-instrumental temperatures including warmth during Medieval and Roman times....

State-of-the-art coupled general circulation model (CGCM) simulations and high-resolution climate reconstructions rarely extend beyond the past few hundred years, limiting possibilities to evaluate low-frequency temperature fluctuations beyond broad assessments (and debate) of the Medieval Warm Period and Little Ice Age⁴. In fact, most high-resolution temperature reconstructions¹⁶ including tree-ring width (TRW) records, the most widespread and important late-Holocene climate proxy¹⁷,

• have never even been compared with orbital forcing....

We here address these issues by developing a 2,000-year summer temperature reconstruction based on 587 high-precision maximum latewood density (MXD) series from northern Scandinavia (Fig. 1). The record was developed over three years using living and subfossil pine (Pinus sylvestris) trees from 14 lakes and 3 lakeshore sites >65° N (Methods), making it not only longer but also much better replicated than any existing MXD time series (for example, the widely cited Tornetraesk record contains 65 series¹⁹)."...

via Tom Nelson