Accurate ENSO records more than a few decades old are rare - although modern reinterpretations of the instrumental record might change this somewhat.
Some proxies rely on tree or coral rings - biological - about 450 years max and not hugely accurate. http://onlinelibrary.wiley.com/doi/10.1002/jqs.1297/pdf Other proxies rely on deposition in cores - see Figure 4 of the following. It 'suggests' a change 5000 years BP - which is interesting in terms changes of African rainfall. Please note the language below - climate is by no means linear. 'This is a proxy record based on the distribution of inorganic clastic laminae in a core retrieved from Lake Laguna Pallcacocha in Ecuador. The laminae are deposited during ENSO-driven episodes of alluvial deposition in the Laguna Pallca10 cocha drainage basin. These laminae are mixed with dark-colored organic-rich silt. The surface of the core sections was scanned and the intensity of the red color was used to generate the proxy record. In general higher intensity values correspond to El Ni˜no and lower values to La Ni˜na. This record has been extensively analyzed and recent results (Moy et al., 2002; Tsonis, 2008) suggest a change in the dynamics at around 3000 BC. 15 It appears that around that time a bifurcation occurred in the ENSO system causing the attractor of the underlying dynamical system to become higher dimensional with less stable behavior (Tsonis, 2008). As a consequence the system switched from a dynamics where the normal La Ni˜na condition was the dominant mode to a dynamics where El Ni˜nos became more frequent and stronger. Changes in boreal summer in20 solation or slow changes in ocean dynamics (which are known to be affected during interglacial events) have been suggested as possible mechanisms for this bifurcation (Tsonis, 2008).'http://www.clim-past-discuss.net/6/801/2010/ cpd-6-801-2010-print.pdf On Sep 21, 8:21 am, "David B. Benson" <[email protected]> wrote: > On Sep 19, 11:56 pm, Robert I Ellison <[email protected]> > wrote:> ... > > > We barely know what ENSO was doing 400 years ago ... > > There is a good proxy for the past 10,000 years. > > But I fear you have fallen into the fallacy of > reductionism. Instead, concentrate on longer > time scales. A good beginning is W.F.Ruddiman's > "Earth's Climate: Past and Future" with its fine > and simple exposition of relevant time scales; > decadal. centennial and millennial. > > Then use some linear system theory to consider > the climate's response to the (approximately) > ramp function of additional forcing over the past > 130+ years, a centennial scale. -- You received this message because you are subscribed to the Google Groups Global Change ("globalchange") newsgroup. Global Change is a public, moderated venue for discussion of science, technology, economics and policy dimensions of global environmental change. Posts will be admitted to the list if and only if any moderator finds the submission to be constructive and/or interesting, on topic, and not gratuitously rude. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/globalchange
