Climate change in New Mexico reflects the effects of human-caused increases in atmospheric carbon dioxide. According to the U.S. Environmental Protection Agency, most of the state has warmed at least one degree Fahrenheit over the last century; across the southwestern United States, heat waves are becoming more common and snow is melting earlier in spring. In coming decades, climate change is likely to reduce flows in the Colorado, Rio Grande, and other rivers; threaten livestock health; increase the frequency and intensity of wildfires; and convert some rangelands to desert. New Mexico is experiencing higher temperatures and a drier climate.

Snowpack: As the climate warms, less precipitation falls as snow and more snow melts during winter, so the amount of accumulated snow is decreasing. Since the 1950s, snowpack has declined in New Mexico and in Colorado, Utah, and Wyoming—the headwaters of the Rio Grande, San Juan, Colorado, and Navajo rivers. Diminishing snowpack in northern New Mexico will shorten the season for skiing and other winter recreation and may allow subalpine fir and other high-altitude trees to grow at higher elevations, shifting the tree line. A higher tree line would decrease the extent of alpine tundra ecosystems, which could threaten some species. Water availability: the changing climate is likely to increase the need for water but reduce the supply. Warmer temperatures increase the rate at which water evaporates (or transpires) into the air from soils, plants, and surface waters, so irrigated farmland would need more water. But less water is likely to be available because precipitation is unlikely to increase enough to make up for the additional water lost to evaporation. Annual rainfall is more likely to decrease than increase, so soils are likely to be drier and periods without rain longer, making droughts more severe.

The decline in snowpack could further limit the supply of water for some purposes. Mountain snowpacks are natural reservoirs: they collect winter snow and release water when the snow melts in spring and summer. Over the past 50 years, snowpack has been melting earlier in the year. Dams capture most meltwater and retain it for use later in the year, but upstream of these reservoirs less water is available during droughts for ecosystems, fish, water-based recreation, and landowners who draw water directly from flowing rivers. Due to climate change, New Mexico's water resources have declined. In 2019, the Center for Biological Diversity named New Mexico's Gila River the nation's most endangered river because of climate change. Agriculture: Increasing droughts and higher temperatures are likely to interfere with New Mexico’s farms and cattle ranches. Hot weather can threaten cows’ health and cause them to eat less, grow more slowly, and produce less milk. Livestock operations could also be impaired by fire and changes in the landscape from grassland to woody shrubs more typical of a desert. Reduced water availability would create challenges for ranchers, as well as farmers who irrigate fruits, vegetables, pecans, and other nut trees.

Wildfires and changing landscapes: Higher temperatures and drought are likely to increase the severity, frequency, and extent of wildfires, which could harm property, livelihoods, and human health. On average, more than 2 percent of the land in New Mexico has burned per decade since 1984. Wildfire smoke can reduce air quality and increase medical visits for chest pains, respiratory problems, and heart problems. The combination of more fires and drier conditions may expand deserts and otherwise change parts of New Mexico’s landscape. Many plants and animals living in arid lands are already near the limits of what they can tolerate. A warmer, drier climate would generally extend the Chihuahuan Desert to higher elevations and expand its geographic range. In some cases, native vegetation may persist and delay or prevent expansion of the desert. In other cases, fires or livestock grazing may accelerate the conversion of grassland to desert in response to the changing climate. For similar reasons, some forests may change to desert or grassland.

Pests: Warmer, drier conditions make forests more susceptible to pests. Drought reduces trees' ability to defend against attacks from pests such as bark beetles, which have infested 200,000 acres in New Mexico. Temperature controls the life cycles and winter mortality rates of many pests. With higher winter temperatures, some pests can persist year-round, and new pests and diseases may become established.

Extreme heat: Hot days can be unhealthy—even dangerous. Certain people are especially vulnerable, including children, the elderly, the sick, and the poor. High air temperatures can cause heat stroke and dehydration, and affect cardiovascular, respiratory, and nervous systems. Higher temperatures are amplified in urban settings where paved and other surfaces store heat. Warmer air can also increase the formation of ground-level ozone, a key component of smog. Construction crews may increasingly operate on altered schedules to avoid the heat of the day.

New Mexico is part of the Southwest region. Since the 1970s, New Mexico's average temperature has risen by 2.7 degrees Fahrenheit, in part because of increased greenhouse gas emissions. This makes the Southwest the hottest and driest region in the United States. Climate change threatens the natural resources and public health of tribal communities. Rising temperatures and increasing drought are likely to decrease the availability of certain fish, game, and wild plants on which the Navajo and other tribes have relied for generations. Water may be less available for domestic consumption, especially for those who are not served by municipal systems or reliable wells; about 30 percent of the people on the Navajo Nation must haul water to meet daily needs. Recurring drought and rising temperatures may also degrade the land itself. On the Arizona portion of the Navajo Nation, for example, the Great Falls Dune Field has advanced almost a mile in the last 60 years, threatening roads, homes, and grazing areas.