The lifetime of excess atmospheric carbon dioxide

We explore the effects of a changing terrestrial biosphere on the atmospheric residence time of CO2 using three simple ocean carbon cycle models and a model of global terrestrial carbon cycling. We find differences in model behavior associated with the assumption of an active terrestrial biosphere (forest regrowth) and significant differences if we assume a donor-dependent flux from the atmosphere to the terrestrial component (e.g., a hypothetical terrestrial fertilization flux). To avoid numerical difficulties associated with treating the atmospheric CO2 decay (relaxation) curve as being well approximated by a weighted sum of exponential functions, we define the single half-life as the time it takes for a model atmosphere to relax from its present-day value half way to its equilibrium pCO2 value. This scenario-based approach also avoids the use of unit pulse (Dirac Delta) functions which can prove troublesome or unrealistic in the context of a terrestrial fertilization assumption. We also discuss some of the numerical problems associated with a conventional lifetime calculation which is based on an exponential model. We connect our analysis of the residence time of CO2 and the concept of single half-life to the residence time calculations which are based on using weighted sums of exponentials. We note that the single half-life concept focuses upon the early decline of CO2under a cutoff/decay scenario. If one assumes a terrestrial biosphere with a fertilization flux, then our best estimate is that the single half-life for excess CO2 lies within the range of 19 to 49 years, with a reasonable average being 31 years. If we assume only regrowth, then the average value for the single half-life for excess CO2 increases to 72 years, and if we remove the terrestrial component completely, then it increases further to 92 years

Stock market co-movement in the Caribbean

This paper investigates co-movement in five Caribbean stock markets (Barbados, Jamaica and Trinidad and Tobago, The Bahamas and Guyana) using common factor analysis. The common factors are obtained using principal component analysis and therefore account for the maximum portion of the variance present in the stock exchanges investigated. We break our analysis down and test for co-movement in different periods so as to ascertain any changes that have taken place from one period to the next. In particular we examine 10-year, 5-year and 3-year periods. We also specify a vector autoregression model and test for co-movement between the five markets during the sample period through impulse response functions. Both of our tests fail to find any evidence of co-movement between the exchanges over the entire sample period. However, we find evidence of periodic co-movement, particularly between exchanges in Barbados, Jamaica and Trinidad and Tobago

Working Effectively with People who are Blind or Visually Impaired

This brochure on peoples who are blind or visually impaired and The Americans with Disabilities Act (ADA) is one of a series on human resources practices and workplace accommodations for persons with disabilities edited by Susanne M. Bruyère, Ph.D., CRC, SPHR, Director, Program on Employment and Disability, School of Industrial and Labor Relations – Extension Division, Cornell University

Remote sensor imagery in urban research - Some potentialities and problem

Imaging techniques of urban data collection for development and plannin

Rich States, Poor States: ALEC-Laffer State Economic Competitiveness Index

Ranks states' business climates based on income, population growth, and employment and outlook based on current tax policies; analyzes their fiscal conditions; reviews 2010 fiscal reform initiatives; and recommends policies to spur economic growth

Melting of Branched RNA Molecules

Stability of the branching structure of an RNA molecule is an important condition for its function. In this letter we show that the melting thermodynamics of RNA molecules is very sensitive to their branching geometry for the case of a molecule whose groundstate has the branching geometry of a Cayley Tree and whose pairing interactions are described by the Go model. Whereas RNA molecules with a linear geometry melt via a conventional continuous phase transition with classical exponents, molecules with a Cayley Tree geometry are found to have a free energy that seems smooth, at least within our precision. Yet, we show analytically that this free energy in fact has a mathematical singularity at the stability limit of the ordered structure. The correlation length appears to diverge on the high-temperature side of this singularity.Comment: 4 pages, 3 figure