Since the first Earth Day fifty years
ago,
researchers have made tremendous strides
in understanding our complex planet.
Working together, engineers and
scientists have harnessed technology to
make first-ever measurements of the
Earth and our environment. Taking
advantage of instrumented satellites and
the unique vantage point of space, today
we are observing the Earth in more
detail and looking at more processes and
variables than ever before in human
history. Our scientific satellites are
taking the pulse of the planet
everywhere and all of the time.
Scientists and policy makers are using
the satellite measurements to learn
about how our Earth works --
how the many processes on land, in the
atmosphere and in the ocean interact
with each other to create our present
environment, how those interactions will
change as the climate evolves, and how we
as humans can alter what we are doing
today in order to safeguard our planet
for future generations. Thanks to
satellites and to science we now know
much more about the Earth than we did on
the first Earth Day fifty years ago when
I was just 15 years old. Let me give you
some examples of questions that we can
answer today but that we couldn't answer
then on the first Earth Day. We didn't
know quantitatively whether and how
global sea level was changing. We only
had records from scattered coastal tide
gauges. Today, from more than 27 years of
data obtained by exquisitely precise
satellite instruments flown by NASA and
our international partners, we know with
precision and accuracy that global sea
level is relentlessly rising. The
satellite instruments that we use to
measure global sea level are so
sensitive that if we were to put them in
an airplane flying at 40,000 feet, they
would be able to detect the bump caused
by a dime coin lying on the ground. From
these decades of continuous satellite
observations, we know that the global
average sea level is rising three point
four millimeters per year and the rate
seems to be increasing. Tven more
importantly, from those satellite
measurements of sea level and separate
satellite observations of gravity
changes, which are related to changes in
the amount of water in the oceans, we
know which processes are causing sea
level rise. Nearly two-thirds of the
observed rise results from adding water
to the ocean by melting ice sheets and
glaciers on land as surface temperatures
around the globe increase. The satellite
data tell us though that more than a
third of sea level rise is the result of
heating the upper portions of the ocean,
which causes the water to expand, just
like the fluid in an old-fashioned
thermometer expands when temperatures
increase. So thanks to decades of precise
global satellite observations, we know
that the changing climate is resulting
in global sea level rise, and we know how
much of the rise is the result of
putting more water into the ocean and
how much of the rise is the result of
heating the upper ocean. With so much of
humanity worldwide living in coastal
areas and with so much of our nation's
economic and defense infrastructure
located near present-day sea level, the
climate induced rising ocean will have a
significant impact on civilization and
on our nation. On that first Earth Day,
scientists knew that long-lasting
greenhouse gases in the atmosphere
influence our planet's overall radiation
balance. Whether the Earth warms by
trapping some of this
energy or whether it cools by radiating
out more energy than is absorbed
by the Sun, they knew the human burning
of fossil fuels -- coal, oil and natural gas --
increase the atmospheric concentration
of carbon dioxide and other potent
greenhouse gases and also likely caused
the planet to warm. But we didn't know
how much of the human burned greenhouse
gases stayed in the atmosphere, and we
didn't know the ways in which natural
processes control exchanges of carbon
dioxide between the atmosphere on the
one hand and the land and ocean on the
other hand. Indeed at that time, some
people thought that almost all of the
human caused CO2 that didn't stay in the
atmosphere was taken up by vegetation on
land.
Thanks to satellite missions such as the
Orbiting Carbon Observatories 2 and 3
from NASA and international partners
such as Japan, we can now measure and
monitor atmospheric carbon dioxide
levels globally with high space and time
resolution. These measurements from truly
cutting-edge instruments show how our
planet breathes, with land vegetation and
phytoplankton in the ocean taking CO2
from the atmosphere during the sunlit
growing seasons, while putting some CO2
back into the atmosphere during our dark
winter seasons. Indeed by analyzing the
satellite and other measurements, Earth
scientists now know that on average only
about half of the human-caused CO2 from
fossil fuel-burning stays in the
atmosphere, while the other half is taken
up almost equally by the oceans and the
land vegetation. The satellite
measurements are helping us understand
remaining open questions, such as
why some years almost all of the human-
caused
CO2 remains in the atmosphere while
other years almost none of it does.
Our planet is complicated, but detailed
global long-term satellite measurements
are giving us insights into processes
that have been mysteries for all of
human history to date. On the first Earth
Day and even until the start of the 21st
century,
no one knew how much rain fell on our
planet.
Scattered rain gauges on land provided
important information,
but 73% of the planet is covered by
water, and it is not possible to make
accurate rain rate and amount
measurements on oceans and large lakes.
Today, however, thanks to precision
measurements from joint NASA and
Japanese satellites such as the Tropical
Rainfall Mapping Mission, launched in
1997, and the Global Precipitation
Measurement Core Observatory, launched in
2014, and still operating today, as well
as thanks to instruments on more than 10
other satellites that together form the
Global Precipitation constellation, NASA
researchers are routinely producing
global rain and snowfall maps with
spatial resolutions of 6 to 12 miles and
time resolution of an hour or less. This
information, which can only be obtained
from combining observations from many
satellites all orbiting at the same time,
is improving severe weather and flood
warnings and weather forecasts around
the world. Thanks to long-term global
frequent high-resolution satellite
measurements of many different
environmental variables, today researchers
and decision makers alike have available
observations and understanding that
could only be hoped for 50 years ago, on
the first Earth Day. NASA,
US agencies and international partners
across the globe are planning, building
and launching even more and more capable
Earth-observing satellites. All of us
have the responsibility to help advance
the technological and Earth science
revolutions that together have given us
such insight into our complex planet, and
it will improve the lives of every human
during the next 50 years and beyond
EXPLORE EARTH|NASA