Bertrand was investigating the effect of solar and
volcanic influence on climate and concluded «these are clearly not sufficient to explain the observed 20th century warming and more specifically the warming trend which started at the beginning of the 1970s».
The Hansen paper is an extreme case, combining a strong volcanic forcing with a model with high sensitivity, and so probably provides an upper bound for
the volcanic influence on temperature.
Not exact matches
We already know that climate change has a hold
on Earth's surface processes, such as erosion and fluctuations in sea levels... but do surface processes in turn have an
influence on volcanic activity?
These results, which you can read all about in the journal Nature Geoscience, reveal the
influence of surface processes — largely controlled by climate —
on volcanic activity.
In years
influenced by
volcanic eruptions, Nile flooding was generally diminished, leading to social stress that could trigger unrest and have other political and economic consequences,» says Joseph Manning, lead author
on the paper and the William K. & Marilyn Milton Simpson Professor of History and Classics at Yale.
Molten rock (or magma) has a strong
influence on our planet and its inhabitants, causing destructive
volcanic eruptions and generating some of the giant mineral deposits.
One just included the effective
influence on temperatures from manmade forces (including greenhouse gases and aerosols, which tend to have a cooling effect), while the second included both manmade and natural ones (including
volcanic activity and solar radiation).
For
volcanic, there may be some overestimating of historical
influences, as the
influence of temperature and reduced solar input (less insolation)
on tree rings is hardly to separate.
Additional eruptions added from tree ring data reported in Table 2 of Briffa, KR, PD Jones, FH Schweingruber & TJ Osborn, 1998,
Influence of
volcanic eruptions
on Northern hemisphere summer temperature over the past 600 years: Nature 393, 450 - 455.
The uncertainty in the overall amplitude of the reconstruction of
volcanic forcing is also important for quantifying the
influence of volcanism
on temperature reconstructions over longer periods, but is difficult to quantify and may be a substantial fraction of the best estimate (e.g., Hegerl et al., 2006a).
Additional eruptions added from tree ring data reported in Table 2 of Briffa, KR, PD Jones, FH Schweingruber & TJ Osborn, 1998,
Influence of
volcanic eruptions
on Northern hemisphere summer temperature over the past 600 years: Nature 393, 450 - 455.
Any change in the strength of natural (
volcanic, solar)
influences based
on historical variations will have an opposite effect
on the
influence of greenhouse gases, and thus
on man - made emissions.
For
volcanic, there may be some overestimating of historical
influences, as the
influence of temperature and reduced solar input (less insolation)
on tree rings is hardly to separate.
Re # 92:... reconstructions based only
on tree rings may overestimate the
influence of
volcanic eruptions, as not only the temperature is reduced, but there is also a change in direct and diffuse incoming sunlight...
If one takes the MBH98 / 99 reconstruction as base, the variation in the pre-industrial period was ~ 0.2 K, of which less than 0.1 K (in average) from
volcanic eruptions, the rest mostly from solar (I doubt that land use changes had much
influence on global temperatures).
IIRC, long - term
volcanic forcing is negligible, and solar
influence is not a major factor (15 %
on decadal time scales according to Trenberth).
A true «prediction» can't be made because the result will depend
on the future
volcanic eruptions and other
influences on albedo, but you can run the model for each of a couple dozen stochastic processes for the future
volcanic activity.
We instead conclude that solar forcing probably had a minor effect
on Northern Hemisphere climate over the past 1,000 years, while,
volcanic eruptions and changes in greenhouse gas concentrations seem to be the most important
influence over this period.
Vernier, J. - P., L.W. Thomason, et al. 2011: Major
influence of tropical
volcanic eruptions
on the stratospheric aerosol layer during the last decade.
In the text: «These simulations suggest that solar and
volcanic forcing (Fan et al., 2009; Liu et al., 2009a; Man et al., 2012) may exert only weak regional
influences on monsoon systems.»
Bradley, R.S. and England, J., 1978:
Influence of
volcanic dust
on glacier mass balance at high latitudes.
The origin of the 1400 - period begins with the 1998 paper in Nature «
Influence of
volcanic eruptions
on northern hemisphere summer temperature over the past 600 years» As the title suggests, the paper is primarily about identifying eruptions with spikes in the record.
Their workings discount natural
influences; solar radiation, clouds,
volcanic eruptions, ocean currents PDO / AMO as having any real effect
on the climate.
There is also another paper in discussion
on the pitfalls of assuming you can remove solar /
volcanic / ENSO
influences with any confidence.
Scientists have already speculated that
volcanic cycles
on land emitting large amounts of carbon dioxide might
influence climate; but up to now there was no evidence from submarine volcanoes.
The
influence of
volcanic activity
on the climate is indubitable.
Alex's simple model is worthy of further refinement to accommodate the
influence of solar fluctuations,
volcanic activity, changes in GHG and the
influence of clouds, My hunch is that while these factors
on their own would have a relatively minor effect
on climate trends, they may impact much more when their incidence is synchronised.
http://www.agci.org/docs/lean.pdf «Global (and regional) surface temperature fluctuations in the past 120 years reflect, as in the space era, a combination of solar,
volcanic, ENSO, and anthropogenic
influences, with relative contributions shown in Figure 6.22 The adopted solar brightness changes in this scenario are based
on a solar surface flux transport model; although long - term changes are «50 % larger than the 11 - year irradiance cycle, they are significantly smaller than the original estimates based
on variations in Sun - like stars and geomagnetic activity.
«Because the effects of
volcanic eruptions and of ENSO are very short - term and that of solar variability very small, none of these factors can be expected to exert a significant
influence on the continuation of global warming over the coming decades.
The largest natural
influences on the global temperature are the 11 - year solar cycle,
volcanic activity, and the El Nino Southern Oscillation (ENSO).
Major
volcanic eruptions have a short - term cooling
influence on climate due to the particulate haze they cause.
Forster et al. (2007) described four mechanisms by which
volcanic forcing
influences climate: RF due to aerosol — radiation interaction; differential (vertical or horizontal) heating, producing gradients and changes in circulation; interactions with other modes of circulation, such as El Niño - Southern Oscillation (ENSO); and ozone depletion with its effects
on stratospheric heating, which depends
on anthropogenic chlorine (stratospheric ozone would increase with a
volcanic eruption under low - chlorine conditions).
From solar min to solar max the
influence on temp has been estimated at around 0.1 deg C (some scientists came to 0.2), and the LIA was at least partly
influenced by a sustained period of low solar activity, combined with high
volcanic activity (see eg the wikipedia link I provided in the blog post).