Geoscience Reference
In-Depth Information
range.of.spatial.and.temporal.scales..Ecological.systems.have.evolved.to.selectively.
take. advantage. of. regularities. in. physical. environmental. drivers. (such. as. climate).
across.a.very.large.range.of.scales,.and.in.addition.must.respond.to.more.stochas-
tic.variability.in.both.space.and.time.of.these.drivers,.also.across.a.broad.range.of.
scales,.from.that.of.a.stomate.or.needle.(1.mm).to.the.globe.(10,000.km),.a.range.of.
scales.that.encompasses.approximately.7-10.orders.of.magnitude.
T
emperaTure
V
ariabiliTy
and
C
hange
Studies.of.variability.and.change.in.climate.variables.utilize.several.common.gridded.
datasets..Station.data.are.the.basis.for.all.of.these.datasets,.which.make.use.of.different.
ways.of.aggregating.or.averaging.station.data.over.regions..Here.we.use.gridded.0.5°.
(longitude).×.0.5°.(latitude).annual.mean.temperature.data.from.CRUv2.1.(Brohan.et.
al..2006),.which.have.been.widely.used.in.global-trends.analyses..We.use.a.domain.
from.the.Paciic.Ocean.to.107.5°.west.longitude,.and.from.30.to.52.5°.north.latitude,.
and.select.the.longest.period.for.which.all.grid.points.have.complete.records:.the.1920-
2008.period.of.record..Figure 1.2.shows.the.trends.in.annual.mean.temperature.from.
the.HadCRU.dataset..There.are.a.few.patches.of.negative.trends.over.this.time.period,.
but.for.most.of.the.western.United.States,.the.trends.have.been.upward.
In.order.to.better.understand.the.time.dimension.of.these.changes,.we.regionally.
average.the.HadCRU.data.to.produce.a.West-wide.annual.mean.temperature.each.year..
Only.HadCRU.grid.points.with.at.least.some.data.in.the.irst.5.and.last.5.years.are.
used.. We. also. use. the. regionally. averaged. temperature. data. from. WestMap. (www.
cefa.dri.edu/Westmap).derived.from.the.PRISM.dataset.(Daly.et.al..2008)..These.two.
datasets. are. derived. from. different. station. data. and. give. somewhat. different. results.
that.depend.on.how.elevation-temperature.relationships.are.treated,.resulting.in.a.sys-
tematic.difference.stemming.from.systematic.station-grid.elevation.differences..The.
time.series.for.the.regionally.averaged.temperature.(Figure 1.3).shows.a.strong.upward.
trend,.relecting.the.warming.of.the.West.during.the.time.period.of.analysis..The.mag-
nitude.and.frequency.of.negative.anomalies.dwindled.during.the.1970s.and.1980s,.as.
nearly.every.year.since.1985.has.been.near.average.or.above.average.in.temperature..
The.record.warmest.year.remains.1934.but.the.warmest.10-.and.20-year.periods.are.
recent..The.two.time.series.differ.the.most.in.the.early.years.and.consequently.have.
different. trends. (0.6°C. for. HadCRU. and. 1.0°C. for. WestMap).. Slow. variations. high-
lighted. by. the. (smoothed). curves. are. substantially. the. same,. with. a. bit. of. warming.
between.about.1910.and.1930,.fairly.level.temperatures.until.1970,.and.then.warming.
d
ependenCe
of
T
rends
on
e
leVaTion
For.the.mountainous.West,.a.critical.question.about.long-term.change.concerns.the.
relative.rates.of.warming.at.mountaintops,.mid-slopes,.and.valley.loors..Do.these.
rates.differ,.and.if.so,.do.they.vary.among.the.seasons?.Whether.these.rates.should.
be.similar.depends.ultimately.on.the.physical.mechanisms.for.potential.variation.in.
rates. across. elevations.. Unfortunately,. long-term. climate. stations. in. mountainous.
regions. are. fairly. rare:. for. example,. the. state. of. Washington. has. no. climate-qual-
ity.stations. above. 1300.m.that. provide.full.annual.measurements.before. 1945.and.
