New fire histories in the northeastern U.S. are described by fire scarred trees and stumps, variable fire scar landscapes, fire probabilities, and mean fire intervals. Dated fire scars derived from 8 fire history sites in the Northeast and 179 elsewhere (over 3,000 trees) were used to document, calibrate, and predict rates of ecosystem combustion. An ecosystem combustion model (PC2FM1) that uses fire rate data, atmospheric variables (temperature, H2O, and O2), and a reactant concentration can be used as a proxy to estimate fire frequency in the diverse climates and landscapes of the Northeast. Since much of the fire scar data in the Northeast is spatial limited by rapid wood decay, logging, and burning, modeling allows for detailed spatial climate-fire estimates at finer landscape scales. Modeling the influence of climate on wildland fire rates allows the prediction of both past and future fire probability in the Northeast based on past and future climate data (global climate models). Future estimates of fire probability are expected to increase in cooler northern and high elevation regions, but decrease slightly in some hotter and drier regions. The Northeast, with dense fuels (reactants) and rising temperatures (reaction environment), is expected to see an increase of up to 80 percent in fire probability compared to current conditions2. In the Northeast, the centuries-long fire record and modeling with the basic principles of physical chemistry will increase prediction efforts.