Average annual temperature has increased by about 2°F since the 1970s, and the number of extremely hot days and warm nights has increased. Historically unprecedented future warming is likely.
Key Message 2
The summer monsoon rainfall, which provides much needed water for agricultural and ecological systems, varies greatly from year to year and future trends in such precipitation are highly uncertain.
Key Message 3
Droughts are a serious threat in this water-scarce state. Drought intensity is projected to increase and snow- pack accumulation is projected to decrease, which will pose a major challenge to New Mexico’s environmental, agricultural, and human systems. Wildfire frequency and severity are projected to increase in New Mexico.
Figure 1: Observed and projected changes (compared to the 1901–1960 average) in near-surface air temperature for New Mexico. Observed data are for 1900–2018. Projected changes for 2006–2100 are from global climate models for two possible futures: one in which greenhouse gas emissions continue to increase (higher emissions) and another in which greenhouse gas emissions increase at a slower rate (lower emissions)<sup>1</sup>. Temperatures in New Mexico (orange line) have risen about 2°F since the beginning of the 20th century. Shading indicates the range of annual temperatures from the set of models. Observed temperatures are generally within the envelope of model simulations of the historical period (gray shading). Historically unprecedented warming is projected during the 21st century. Less warming is expected under a lower emissions future (the coldest years being about 1°F cooler than the hottest year in the historical record; green shading) and more warming under a higher emissions future (the hottest years being about 10ºF warmer than the hottest year in the historical record; red shading). Source: CICS-NC and NOAA NCEI.<br><br><sup>1</sup>Technical details on models and projections are provided in an appendix, available online at: <a href="https://statesummaries.ncics.org/pdfs/TechInfo.pdf">https://statesummaries.ncics.org/pdfs/TechInfo.pdf</a>.
New Mexico encompasses a large geographic area of diverse
interior-continental environments, including mountain ranges,
forests, grasslands, and deserts. Temperature varies widely across
the state. Monthly average temperatures in the northern mountainous
regions range from the low 20s in January to around 60 in July while
in the lower elevations in the south the range is from middle 40s
in January to low 80s in July. Much of the state is characterized
as arid to semi-arid with most areas in the central and west receiving
less than 15 inches of precipitation annually.
The last decade has been the warmest on record for the state
(Figure 1), with increasing trends in both extremely hot days and
warm nights. Over the past several decades, much of the state has
seen increases in the number of extremely hot days (maximum temperature
at or above 100°F; Figure 2), most prominently in the eastern plains.
A similar trend is apparent in the number of warm nights (minimum
temperature at or above 70°F; Figure 3), which has increased since
the mid-1970s, and in winter temperatures, as the number of very
cold nights (minimum temperature at or below 0°F) was below average
during the 1990–2009 and 2015–2018 periods (Figure 4a).
Precipitation is highly variable from year to year, and
decade to decade. Statewide annual precipitation has
ranged from a high of 26.57 inches in 1941 to a low of
6.58 inches in 1956. The wettest multi-year periods
were in the early 1940s and mid-1980s (Figure 4b)
with the wettest 5-year period being 1984–1988. The
driest multi-year periods were in the early 1950s and
early 2010s (Figure 4b) with the driest 5-year period
being 1952–1956. Multi-year periods of high and low
precipitation have resulted in very large swings in
reservoir supplies for agriculture. Levels in the Elephant
Butte Reservoir were high from the 1920s to the 1940s
before dropping to low levels until the 1980s. High levels
remained throughout the 1980s and 1990s until falling
again in the first part of the 21st century (Figure 5). This
illustrates that there have been extended (decades-long)
periods of unusual wet or dry conditions. The latest
multi-year drought (2011–2014; the second-worst
statewide drought since the early 1950s) resulted in
near record low levels of water in the reservoir.
Figure 2: The observed number of extremely hot days (annual number of days with maximum temperature at or above 100°F) for 1900–2018, averaged over 5-year periods (bars; last bar represents 4-year average). Filled circles connected by black line segments show annual values. The horizontal black line shows the long-term average for 1900–2018 is 10.7 days per year. These values are averages from eight long-term reporting stations. Since 1990, the number of extremely hot days has on average risen in New Mexico although not all locations have experienced increases. The largest number of days was recorded in the 2010–2014 5-year period, with the eight long-term stations averaging 17 days per year over 100°F. Source: CICS-NC and NOAA NCEI.
Unlike many areas of the United States, New Mexico has not
experienced an upward trend in the frequency of extreme
precipitation events; although the value for the 2015 to 2018
period was the highest on record, it is too short a period to
constitute a trend (Figure 4c). The annual number of extreme
precipitation events (days with precipitation of 1 inch or more)
has been variable over the past three decades, fluctuating in
a similar fashion to the pronounced variations in total annual
precipitation (Figure 4b). Since drought conditions began
in the 2000s, the occurrence of these events was near or
below average until the 2015–2018 period, with a higher than
average number of events.
Figure 3: The observed number of warm nights (annual number of days with minimum temperature at or above 70°F) for 1900–2018, averaged over 5-year periods (bars; last bar represents 4-year average). Filled circles connected by black line segments show annual values. The horizontal black line shows the long-term average for 1900–2018 is 5.9 nights per year. These values are averages from eight long-term reporting stations. The frequency of warm nights has risen dramatically in the last two decades, with the 2010–2014 5-year period and the 2015–2018 4-year period experiencing about double the long-term average. Source: CICS- NC and NOAA NCEI.
An important feature of New Mexico’s summer climate
is the North American Monsoon, which causes July and
August to be the wet season across much of the state
(Figure 4d). In some regions of the state, monsoon rainfall
accounts for half of the annual precipitation and plays an
important role in supporting the agricultural economy. The
monsoon rains are highly beneficial, but can occasionally
be destructive. In 2006, a remarkably persistent monsoon
regime was in place from late July through most of August,
and caused significant damage and flooding in southern
New Mexico. This was seen again in the summer of 2013
when a single, very wet week in September caused major
flooding across the central and western portions of the
state. These events provided much-needed water for the
reservoirs, but also caused widespread damage.
Figure 4: The observed (a) number of very cold nights (annual
number of days with minimum temperature at or below 0°F), (b) annual
precipitation, (c) number of extreme precipitation events (annual
number of days with precipitation of 1 inch or more), and (d) monsoon
season precipitation, averaged over 5-year periods (bars; last bar
represents 4-year average). Filled circles connected by black line
segments show annual values. The horizontal black line shows the
long-term average. Values for Figures 4a and 4c are averages from
long-term reporting stations, eight for temperature and eleven for
precipitation. The number of very cold nights has been below average
since 1990, with the exception of the 2010–2014 5-year period.
Precipitation is highly variable from year to year. Source: CICS-NC
and NOAA NCEI.
Under a higher emissions pathway, historically
unprecedented warming is projected by the end of the
21st century (Figure 1). Even under a pathway of lower
greenhouse gas emissions, average annual temperatures
are projected to most likely exceed historical record
levels by the middle of the 21st century. However,
there is a large range of temperature increases under
both pathways, and under the lower pathway, a few
projections are only slightly warmer than historical
records. Heat waves are projected to increase in
intensity, posing a risk to human health, while cold wave
intensity is projected to decrease.
Although projections of annual precipitation are
uncertain, precipitation in spring, already the dry
season in New Mexico, is projected to decrease across
most of the state> (Figure 6). Decreased precipitation
in the spring, combined with warmer temperatures,
would have profoundly negative impacts on mountain
snowpack that feeds water supply reservoirs, reducing
water flow to the river basins, which rely on the
snowpack for summer water supplies. Even if snowpack
accumulation were not to decrease, the projected
higher temperatures will lead to an earlier initiation
and earlier end to the snowmelt season, potentially
necessitating changes in water management.
The extended record indicates that droughts are a
frequent occurrence in New Mexico and episodes
more severe than any in the recent historical record
have occurred in the more distant past (Figure 7).
Droughts are projected to become more intense.
Recent drought conditions have negatively impacted
ecosystems across the state. For example, extreme
drought in the Chihuahuan Desert has caused grasslands
to die, decreasing grazing resources for livestock. While
projections of changes in precipitation are uncertain,
higher temperatures will increase water evaporation
from moist and vegetated surfaces. This will reduce
streamflow and soil moisture, increasing the intensity
of naturally occurring droughts. Drought will not only
further challenge limited agricultural resources but also
increase the occurrence and severity of wildfires and the
frequency of dust storms.
Figure 5: Monthly time series of the average water storage levels in the Elephant Butte Reservoir (March 1915–May 2019). Water storage levels in the reservoir have varied widely over the years. Water storage levels were generally low, and in some cases nearly zero, from the late 1940s to early 1980s. Following high levels during the 1980s and 1990s, a large decline occurred in the early 21st century in response to severe drought conditions. In 2004, 2013, and 2018, storage levels approached record lows due to the extended drought. Source: USBR.
Figure 6: Projected change in spring precipitation (%) for the middle of the 21st century compared to the late 20th century under a higher emissions pathway. Hatching represents areas where the majority of climate models indicate a statistically significant change. New Mexico is south of the transition zone from wetter conditions in the north to drier conditions in the south. Southwestern New Mexico is part of a large area of projected decreases that includes Central America, Mexico, and the southwestern United States. Source: CICS-NC, NOAA NCEI, and NEMAC.
Figure 7: Time series of the Palmer Drought Severity Index from the year 1000 to 2018. Values for 1895–2018 (red) are based on measured temperature and precipitation. Values prior to 1895 (blue) are estimated from indirect measures such as tree rings. The thick black line is a running 20-year average. In the modern era, the wet periods of the early 1900s and the 1980s–1990s and the dry period of the 1950s are evident. The extended record indicates periodic occurrences of similar extended wet and dry periods. Source: CICS-NC and NOAA NCEI.
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