We present a compilation of tropospheric ¹⁴CO₂ for the period 1950–2010, based on published radiocarbon data from selected records of atmospheric CO₂ sampling and tree-ring series. This compilation is a new version of the compilation by Hua and Barbetti (2004) and consists of yearly summer data sets for zonal, hemispheric, and global levels of atmospheric ¹⁴C. In addition, compiled (and extended) monthly data sets for 5 atmospheric zones (3 in the Northern Hemisphere and 2 in the Southern Hemisphere) are reported. The annual data sets are for use in regional and global carbon model calculations, while the extended monthly data sets serve as calibration curves for ¹⁴C dating of recent, short-lived terrestrial organic materials.

New records of δ¹³C and Δ¹⁴C values in annual rings of pine and oak from different sites around the world were obtained with a time resolution of 1 yr. The results obtained for Europe (Poland), east Asia (Japan), and South America (Peru) are presented in this paper. The δ¹³C and radiocarbon concentration of α-cellulose from annual tree rings of pine and of the latewood of oak were measured by both accelerator mass spectrometry (AMS) and liquid scintillation spectrometry (LSC). The values of ¹⁴S, which represent decreasing ¹⁴C concentrations caused by the emission of CO₂ from fossil fuel use (Suess effect; Suess 1955), were calculated for each site. Low average ¹⁴S (about −0.4 to 0.8%) values for clean areas and high values (about 3.4–3.6%) for industrial and/or urbanized areas were noted. Records of the δ¹³C values obtained for pine and oak from Poland were used to reconstruct climate changes during the last 400 yr. The results clearly indicate the climate cooling during the periods of the Maunder minimum (1645–1715) and the Dalton minimum (1790–1820). The anti-correlation between the δ¹³C and Δ¹⁴C records during those 2 periods is clear if the ¹⁴C record is shifted toward older ages by 24 yr.

Local reservoir ages are often estimated from the difference between the radiocarbon ages of aquatic material and associated terrestrial samples for which no reservoir effect is expected. Frequently, the selected aquatic material consists of bivalve shells that are typically well preserved in the archaeological record. For instance, large shell middens attest to the importance of mussel consumption at both coastal and inland sites. However, different physiological mechanisms associated with tissue and shell growth may result in differences in reservoir effects between the surviving component (shell) and the component relevant to dietary reservoir effects in consumers (tissue). The current study examines bivalve tissue-shell age differences both from freshwater and marine contexts close to archaeological sites where human consumption of mollusks has been attested. Results exhibited significant ¹⁴C age differences between bivalve tissue and shell in a freshwater context. In a marine context, no significant bivalve tissue-shell age differences were observed. The results also showed that riverine and lacustrine shells show large and variable freshwater reservoir effects. The results have important implications for establishing local reservoir effects especially in a freshwater environment. For good a priori knowledge of expected ¹⁴C differences in organic and inorganic water, carbon is thus necessary. Furthermore, the high variability in freshwater shell ¹⁴C ages implies the need for representative sampling from the archaeological record.