Abstract
This report concisely reviews some aspects climate science, and their relevance to the conclusion of ".. a discernible human influence on global climate .., within the context of the need to balance the magnitude of potential near-term emissions reductions against the certainty of global warming, potential environmental impacts resulting from inaction, and possible adverse economic impacts on the achievement of long-term goals. The review of the state of climate science strongly suggests that a human contribution to the current warming can not yet be proven. For example, the best estimate of the radiative forcing in the atmosphere due to anthropogenic emissions (greenhouse gases and particles) since about 1800 is equivalent to only about 1% of the magnitude of the natural greenhouse effect. It is unknown whether this is a sufficient perturbation to move a thermally equilibrated climate system (dominated by poorly understood feedback mechanisms) in the direction of warming. The situation is further complicated by the recent discovery of numerous regional climate cycles which operate on scales from a few to thousands of years, and our lack of understanding of natural climate variability. These issues,taken either singly or together, greatly confuse the search for identifiable fingerprints of mans impact on climate. It is concluded, therefore, that climate science does not add weight to arguments favoring drastic near-term reductions in emissions.