Future Climate Projections

The New York State Climate Impacts Assessment presents projections of how weather and climate, sea level, and other effects and impacts of climate change are likely to change in the decades ahead. The climate projections were developed specifically for the New York State Climate Impacts Assessment by a team at Columbia University. The Columbia team developed the projections using global climate models from the Coupled Model Intercomparison Project version 6 (CMIP6). These computer models simulate how the Earth’s atmosphere, oceans, and other physical features respond to greenhouse gases in the atmosphere. The CMIP6 models are widely recognized as the best available climate models and have also been used in the global and national assessments of climate change.

Climate Projections Data and Methodology 

The Process 

Columbia’s projections for most variables show how New York’s climate will change compared with a baseline period (1981–2010), which is based on historical observed data at weather stations throughout the state. Sea level was projected for three locations that also have many decades of historical data for comparison.  

Climate projections depend on future heat-trapping greenhouse gas emissions. In other words, to predict how quickly the climate will change, modelers have to make assumptions about how the level of greenhouse gases in the atmosphere will change in the future. That means predicting if countries around the world will continue to produce more greenhouse gas emissions—and how quickly the world adopts renewable energy and other ways to reduce emissions.  

There are many different possibilities. Climate scientists commonly use a set of scenarios called Shared Socioeconomic Pathways (SSPs) to represent these different possibilities. Each SSP includes assumptions about how quickly countries around the world will grow their economies, how much of that growth will be powered by fossil fuels, and how quickly the world takes steps to combat climate change by reducing greenhouse gas emissions. This means each scenario results in some relative level of greenhouse gas emissions, ranging from very low to very high. Scenarios with higher emissions correspond to higher levels of greenhouse gases in the atmosphere. When these emissions numbers are fed into a climate model, the model will show how much warming can be expected and how the climate will change in response. Higher emissions mean more warming and more severe impacts. 

The Assessment’s Projections 

Columbia’s projections generally use results from two scenarios: a “middle-of-the-road” scenario known as SSP2-4.5 (intermediate emissions) and a fossil-fueled development scenario with very high emissions known as SSP5-8.5. Columbia used these scenarios as applied to 35 different climate models developed by a variety of academic and government research centers. This meant the modeling gave 70 different sets of results (35 models for two greenhouse gas emissions scenarios). To make the results more understandable and usable, this assessment provides either the midpoint of all these results (the median) or a range of two numbers (the 25th and 75th percentiles of the distribution of results from individual climate models across both scenarios). Projections were customized for New York using weather stations across the state that have many decades of historical records, to ensure that the modeled projections are applied to an accurate baseline climate.  

When a decade is listed, it usually represents a 30-year average centered on that decade. (For sea level rise, it represents a 10-year average.) For example, “the 2080s” is really the projected average for 2071–2100. Climate scientists use 30-year averages like this to calculate future projections because they largely account for natural year-to-year variability in climate conditions. Most variables were modeled through 2100, which means the 2080s is the latest average available. Sea level projections used a different modeling approach that extended through 2150.  

For topics not included in Columbia’s modeling (for example, some of the discussions on the summary page), the assessment team used the best available projections published in other recent climate assessments or scientific literature. 

It is still important to recognize that the degree of change in these future projections is not inevitable. If the world takes serious action to reduce greenhouse gas emissions and control future warming, the resulting climate changes could be closer to the low end of the projected range, or maybe even lower.