We have a tendency, whether following sports, the stock market or politics, to think the past is a guide to the future. What we are learning is that with climate, this is no longer the case. The pattern we have seen no longer guides us.

We have a tendency, whether following sports, the stock market or politics, to think the past is a guide to the future. What we are learning is that with climate, this is no longer the case. The pattern we have seen no longer guides us.

Last week, I identified temperature projections for the valley. Here, I explore precipitation patterns and other consequences of our future changed climate.

Precipitation projections vary more than temperature projections. Using 1961-1990 averages as the basis for comparison, Rogue Valley average annual projected change for 2035-2045 ranges from about 4 inches less to no change. For 2075-2085 the range is greater: from 5.5 inches less to nearly 12 inches more. Seasonal variability is expected, with the 2035-2045 winter ranging from about 1 to 2 inches more and summer exhibiting about half an inch less. The 2075-2085 winter projection ranges from the current value to nearly 6 inches more while summer ranges from the current to about an inch less. Even if precipitation were to hold steady or increase slightly, hotter conditions will drive greater evaporation, stimulating increased drought.

One additional trend is that mountain precipitation will fall at lower, warmer elevations as rain rather than snow. This continues the past trend towards reduced winter snowpack.

Increased lower elevation rain will likely induce early winter flooding. With warmer temperatures, the snowpack that accumulates will melt earlier, causing stream flow to continue its trend of peaking earlier and earlier in the season. Irrigation water needed for late growing season crops will become severely limited as the century passes.

A second probable pattern is a change to more heavy rainfall days, with fewer light rainfall days. This enhances both floods and droughts with flooding likely as heavy rains falling on dry ground flow over rather than soaking into the soil, thus swelling creeks and rivers.

Another critical issue is timing of snowfall and snowmelt. Projections throughout the mountain West indicate snowpack accumulation will decrease considerably. By 2035-2045, the shortfall may result in just 35 percent to 40 percent of current accumulation. By 2075-2085 snowpack may drop just 10 percent to 20 percent current accumulation. This is critical for human water needs as well as recreation, since late summer agricultural water comes from snowmelt.

By late century, there may be very little fall stream flow. Ironically, water storage infrastructures in the region were constructed expecting that water would be stored in snowpack; with time, melting snowpack will likely no longer be adequate to supply needs.

Increased heat and drought will likely result in continued lengthening of the fire season (already two and a half months longer than 1970) and increased loss from wildfires. Additionally, weather variability will likely increase, bringing more severe storms and snowfalls.

The valley currently exhibits wet winters and dry summers. Likely future lowland climatic conditions will become more appropriate for deciduous forest communities such as oaks and other hardwoods, while higher elevation conditions currently supporting spruce/fir/hemlock communities will be compromised and Douglas fir will likely be reduced. Grassland and scrubland conditions are likely to expand as lowland forest conditions dwindle. As wildfires increase, a continued shift toward more fire-tolerant plant communities is anticipated.

Increased temperature enhances insect and other pest development rates so we can expect increased crop loss to such pests with more invasions of drought-tolerant weeds. Meanwhile, warming aquatic systems coupled with decreasing summer stream flow will threaten cold-water fish — not just because of the temperature (since warm water holds less oxygen than cold water) but also because spawning conditions will be compromised.

Droughts and heat waves have impacts not only on natural systems but also directly on humans — especially on those working outside and more susceptible young and elderly Americans. Increased carbon dioxide in the atmosphere will likely enhance pollen production, a problem for anyone suffering allergies or respiratory difficulties.

Meanwhile, warmer temperatures will probably expand the range of and enhance the development rate of many diseases and disease-bearing organisms — such as insect, water-borne and vector-borne diseases (e.g. malaria and West Nile virus). Increased heat waves and wildfires will reduce air quality, directly affecting younger and older residents, again, especially those with respiratory ailments.

While rising sea level is not a direct threat to this area, its potential impact across the nation and planet may have local consequences. Losses of agricultural and inhabitable land as sea level rises will produce millions of refugees globally. Even as far as we are from the ocean, national and international refugee migrations will likely have an impact on the region.

While the Pacific Northwest will likely be one of the latest regions to suffer extensively from climate change, the impacts are potentially substantial and demand our attention. Next week I will discuss what is happening in the region and what we can do.

Alan Journet, a retired ecologist, lives in the Applegate Valley. He can be reached at alanjournet@gmail.com.