Carbon capture and sequestration (CCS) may play a key role in our energy future. However, the widespread sequestration of CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> into storage reservoirs is inhibited by safety and leakage concerns. Effective leakage monitoring at the surface is recently made possible by the development of quantum cascade (QC) laser-based sensors, which are capable of tracking fluxes in CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> isotope concentrations. In this paper, we initially discuss the status of this technology, including recent results from distributed feedback QC lasers for use in sensing CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> isotopic ratios. These lasers show single-mode emission at 4.32 μm, overlapping strong absorption resonances of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</sup> OCO. We then consider the value of such devices for quantifying CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> leakage using a climate-economy integrated-assessment model that is modified to include CCS. The sensitivity of model outcomes to reservoir leakage is studied, showing that an average reservoir storage half-life on the order of 1000 years or longer can limit atmospheric temperature increases to 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C or less over the next 150 years for economically optimal emissions scenarios. The present day economic value of CCS is established versus reservoir half-life, showing a significant return on investment ( ~ 2 trillion U.S.$, or ~ 4% of gross world product) when the average reservoir half-life is 250 years, with a sharp drop in the value of CCS technology for half-life values below 250 years. Quantifying CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> leakage rates via QC laser-based sensing will contribute greatly toward accurately assessing CCS technology and its efficacy as part of CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> limitation strategies.