Weather instantaneous or synoptic measurements

Climate time / space average

Basic Concepts

“Northern New England Climate: Past, Present, and Future”

Weather - the state of the air and atmosphere at a particular time and place : the temperature and other outside conditions (such as rain, cloudiness, etc.) at a particular time and place

temperature (average energy, ˚C) humidity (water vapor, g/kg) pressure (force/area, mb = 100 N/m2) winds (circulation, m/s) cloud cover (liquid/solid water) precipitation rate (mm/day)

Measurements of the following variables are used to quantify weather

Climate is often defined as ‘average weather’, usually described in terms of the mean and variability of temperature, precipitation and wind over a period of time (typically 30 years).

Climate is also characterized by the frequency and magnitude of extreme weather events

A Definition of Climate

hourly (synoptic)

daily mean daily range (diurnal cycle) monthly mean annual mean annual range (seasonal cycle)

air temperature data

The average, or mean, of a meteorological variable is:Climate defined

And, the variance (a measure of how far a set of numbers is spread out:

average daily temperature

30-year annual average = 51.7˚F

average daily temperature

30-year annual average = 51.7˚F

average daily temperature

average monthly temperature

internal dynamics example -

persistent ridging over western North

America

internal dynamics example - persistent ridging over western North America

average monthly temperature

external forcing example - Mt. Pinatubo

What Factors Are Involved In Changing Earth’s Climate?

Examples of external forcing include: solar variations volcanic eruptions changes in atmospheric composition

The climate system evolves over time under the influence of its own internal dynamics and due to changes in external forcing.

IPCC, FAQ 1.3, Figure 1

✦ by changing the amount of incoming solar radiation

✦ by changing the fraction of solar radiation that is reflected back to space

✦ by altering the longwave radiation from Earth back towards space

Radiative forcing of global climate

IPCC, FAQ 2.1, Figures 1 & 2

•

•

•

•

•

Greenhouse gases increase dramatically since industrial revolution

IPCC, FAQ 2.1, Figure 1

Long-term record of globally averaged annual temperature

+1.2˚F/century

Long-term record of annual average temperature for Massachusetts

Long-term record of annual average precipitation for Massachusetts

Long-term record of annual average temperature for Vermont

Long-term record of annual average precipitation for Vermont

Long-term record of annual average temperature for Maine

Long-term record of annual average precipitation for Maine

Lake ice-out

dates

Average ice-out dates for lakes in Maine come about two weeks earlier than they did in the late 19th century

The length of the growing season in Maine has increased over the last 150 years

-40 to -30ºF -30 to -20ºF -20 to -10ºF -10 to 0ºF 0 to 10ºF

Plant hardiness zones have shifted northward over the past few decades

River flow

Over the past 50 years flow has tended to increase in early spring and decrease in late spring/early summer

Model projections of globally averaged surface temperature for

three emissions scenarios

NCAR climate model

Future climate (21st century)

✦ it has changed ✦ we see the impacts ✦ some of the change thus far is attributable

to human activity ✦ northern New England, like the rest of the

planet will experience significantly more change in the future

✦ the change impacts things that we care about

✦ we would like to predict future climate change

Observational Record of Global and Regional Climate: Key Facts

Summary ✦ Greenhouse gas warming is evident

across northern New England

✦ It will continue, at an accelerated rate

✦ Precipitation across the state is likely to increase, less snow, more rain

✦ Climate will be more variable

Questions?