Variations in the Atmospheric Radiocarbon Concentration over the Past 1300 Years

The 2400-year cycle in atmospheric radiocarbon concentration: bispectrum of 14C data over the last 8000 years

We have carried out power spectrum, time-spectrum and bispectrum analyses of the long-term series of the radiocarbon concentrations deduced from measurements of the radiocarbon content in tree rings for the last 8000 years. Classical harmonic analysis of this time series shows a number of periods: 2400, 940, 710, 570, 500, 420, 360, 230, 210 and 190 years. A principle feature of the time series...

Changes in the atmospheric helium isotope ratio over the past 40 years

science growth in iran over the past 35 years

background : this study was carried out to evaluate activities in different branches of science in iran compared to other countries over the past 35 years. methods : e ssential science indicators (esi ) and web of science from (thomson reuters isi) and scimago journal & country rank (sjr) were searched for scientometrics data . esi indicated place of iran among other countries in all 22 scienti...

Global Climate Variations Over the Past 250 Years: Relationships with the Middle East

We analyze recent global temperature reconstructions over several centuries in time based on calibrations of temperature patterns against global networks of long instrumental and “proxy” data (natural archives such as ice cores, corals, and tree rings), focusing on long-term climatic variations in the Middle East. The pattern of global warming of the past century does not show a strong influenc...

Variations in the Pacific Decadal Oscillation over the past millennium

[1] Hydrologically sensitive tree-ring chronologies from Pinus flexilis in California and Alberta were used to produce an AD 993–1996 reconstruction of the Pacific Decadal Oscillation (PDO) and to assess long-term variability in the PDO’s strength and periodicity. The reconstruction indicates that a 50 to 70 year periodicity in the PDO is typical for the past 200 years but, was only intermitten...