I’ve been thinking about how people say Utah’s winters aren’t as cold as they used to be, and there isn’t as much snow in the valley as there used to be. Well, I found some great data at a site created by Utah State University, allowing me to download min and max temperatures daily for 60 years at my local weather station (Pleasant Grove). There are other data about precipitation and snow accumulation, I think, but at this point, I just took a look at the minimum winter temperatures and the maximum summer temperatures. It’s startling. I’m shocked to see such a marked difference since 1990.
This graph shows winter low temperatures, organized by season. Click it to see a larger image.
Anyway, look what has happened since 1990; we’ve hardly dipped below zero, when previous decades saw extremes regularly go between -5° and -20°. It’s a remarkably sudden change after 1990! When people talk about global warming or climate change, they often speak of average temperatures and the changes are quite subtle, like these quotes from the EPA’s website:
“Since the mid 1970s, the average surface temperature has warmed about 1°F.â€
“The Earth’s surface is currently warming at a rate of about 0.32°F/decade or 3.2°F/century.â€
But looking at these minimum temperatures shows a much more dramatic change. This is obviously of interest to gardeners, since the USDA garden zones we all use are keyed to the lowest minimum temperatures expected in an area. Where I live was a solid zone 5 before 1990 — zone 5 has lowest temps reaching -20°. But since then, it has almost turned into a zone 7, which would have lowest temps at 0°. But since we have dipped below zero a few times, we are really a zone 6 (lowest temps at -10°).
Here’s another chart, showing the maximum summer temperatures. These haven’t moved as much as the minimum winter temps, but they do seem to be rising since 1994. Note that in 60 years, we’ve been over 100° 12 times. But seven of those 12 years have occurred just since 1998.
This is a real concern to me. On the one hand, it’s actually nice that our winters have become milder and more livable. But if this trend continues, it may start melting the mountain snow much sooner in the spring/summer and could harm our water supplies, having a serious impact on our quality of life. Imagine if we couldn’t garden anymore, because there wasn’t enough water. Or if we had to ration water for basic needs in our homes. Without adequate water to live, we might start seeing an exodus of people from Utah, and our economy would go in the tank. And all this has been happening so fast since 1990! It’s somewhat frightening.
Hey Kendal, fellow GardenWebber! Good to see you here. Thanks for the thought-provoking comment. Your comment about water vapor being a better greenhouse gas got me thinking about some thoughts I had ten years ago when a lot of talk was turning to hydrogen fuel cells. They say the primary effluent from them will be water vapor, and they make that sound harmless. But if we start spewing a lot more water vapor into the air, in quantities like our current smog loads, won’t that add to the greenhouse effect?
Anyway, this winter has sure been a cold one, with lots of snow, and when you think of last year’s deep cold, too, I’m wondering if the sudden warming of Utah’s winters is coming to an end. I’m not a global warming doubter, but global warming is supposed to be gradual, and I can’t help but think that the sudden change from 1991 through 2006 may have been related to Mt. Pinatubo or some other temporary factor. I wouldn’t be surprised to see us get colder again but back onto a track of very slow warming.
i often wonder about the whole global warming thing. how much is truth and how much is misconstrued truth (notice i did not say false). i think the whole uptick in average temps is pretty well documented but here is my concern—people are not getting the full interpretation of the facts nor the long-term historical context.
first point, melting the icecaps is not going to flood florida—thanks Al Gore. people really understimate the volume of the world’s ocean. the north pole has no impact on water level and neither does any ice shelf. the only thing that matters is non floating ice—greenland and the antarctic interior. ice is also much less dense than water and therefore has a much greater volume. inches possible, feet not likely to not possible.
another variable is the fact that the mantle (land and seafloor) are floating themselves. north america is still rising after being depressed during the last ice age. how does this figure in? i don’t know. tides are not caused by the moon pulling water, but by the moon pulling the land out of the water (low tide is when the moon is overhead). will more water push down the seafloor and raise the land?
ice also has a cooling reflective quality, and it comes and goes very quickly with very little temperature change. the difference between an ice age and a thaw might only be 3 degrees but when the pendulum tips, it happen quickly. dramatic loss of ice does not mean a dramatic rise in temps.
point two. the earth is historically cold right now. humans are ice age mammals and what we consider hot, most other animals consider optimal. in fact the opposite of an ice age is called a “climate optimum”—does not sound that scary to me. the last climate optimum was just before the mini ice age back in the 11th century. it was during this period that the vikings colonized greenland and grew crops. the norse sagas and some evidence suggest that the northwest passage may have been open and the norse boats may have gone as far as baja california or so i read in an article last year. yet the polar bears survived this lack of ice for a century.
there was another warm period that coincided with a population spike in europe. few degrees change and a snow field is a bean field.
the cretaceous, jurassic and carboniferous periods (long before the industrial revolution i might add) were all about 5 degrees warmer than now. the biomass on the planet during those periods was much higher than it is now, so was the oxygen level in the atmosphere. there were retile at both poles. the planet was covered in forest because it was so much wetter. and this gets me back to ocean levels. if the plant warms there is more evaporation and more precipitation both act to cool the planet, but also lower the water level in the oceans as there is more water in the soil, plants, fresh water systems and atmosphere. remember in recent geological history the sahara had hippos and alligators and the fertile cressent is not that fertile currently. they were different a few thousand years ago. why?
the warm periods don’t cause deserts from my understanding, it is the cold periods when the fresh water and the atmospheric moisture is locked in ice. cold air carries little moisture. this can be illustrated by the el nino years. when the ocean warms, the winters are wetter and more mild as are the summers.
i think if the planet warms we will have a wetter less desert planet rather than the dry one people are so afraid of. some models show a more mild planet with less extremes all round, but that is not news worthy.
the tropics can’t get any warmer, it is just the polar and temperate climates that are changing. it is only the lows that are warming. if the wetter planet model is right, we stand to lose deserts and the hot extremes as well.
as for this carbon scare. where do people think all the carbon came from? plants that were growing in the warmer periods pulled it from the atmosphere and locked it up way back when bacteria was not too good art releasing it. burning the resulting fossil fuel is a restoration of locked up resources in the view of plants. plus CO2 is a terrible greenhouse gas. H2O on the other hand is a great one. the trees rotting after katrina released more CO2 than our cars did that year and Mt Pinatumbo in 1992-93 released decades worth in just a few weeks. don’t get me wrong i am against the use of fossil fuel, but it is for matters of real pollutants, acid rain, mercury and of course politics more than CO2.
i am not sure it is a man made problem (mars is also experiencing polar ice loss), and i am not sure it is even a problem. it might be a blessing to africans. it is change and in all change, there are winners and losers. historically warmer means more winners if you look at biomass as the qualifier.
it really is an interesting topic. i like the data you pulled together. my only point is the alarmist stance people are taking is silly in the geological context. the science as the media reports it is very flawed and one sided. if it bleeds it leads. if it gets people to recycle great! but i personally would much rather hear the whole story all the time. this is completely different rant.
blog on brother.
Thanks for such a well written post. I know for the past several years I have commented on how odd it was that our summer temps were so high. I could not remember a time when growing up here that we had temps above 100. And when we did hit 100 it was something to talk about. Now this makes sense, looking at the time period I refer back to 1980-1997 we really did not break 100.