EEE会議（水素のオゾン層への影響：CIT研究報告）
03/6/17

各位

水素エネルギー問題のついでに、「水素の漏れガスが地球環境、とりわけオゾン層に
影響を与える可能性がある」という注目すべき研究報告が昨日米国で発表されました
ので、ご紹介します。
研究したのはカリフォルニア工科大学（CIT)の研究者チームです。

水素エネルギーを利用した自動車は水蒸気を出すだけで地球環境に優しいというのが
今まで国際的に通説化していますが、もしこの研究報告が正しいとすればまた別の問
題が生ずるということになるのかも知れません。　どなたか専門家のご意見を伺いた
いものです。
金子熊夫

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Subject:  Study Says Hydrogen Leakage could Harm Earth's Ozone Layer
(Society has time to prepare for potential impact of hydrogen economy)


While the proposed hydrogen-fueled cars of the future are generally
considered to be environmentally friendly because they emit only water
vapor, a new study says that leakage of the hydrogen gas that would fuel
such cars might cause problems in the Earth's protective ozone layer.

A June 12 press release says that researchers at the California Institute
of Technology report that the leaked hydrogen gas resulting from a
hydrogen economy, if it accumulates, could indirectly cause as much as a
10-percent decrease in atmospheric ozone. The stratospheric ozone layer
protects the Earth from the sun's ultraviolet radiation, which causes skin
cancer and weakened immune systems in humans.

If hydrogen were to replace all fossil fuels used in transportation and to
power buildings, the scientists estimate that four to eight times more
hydrogen would be released into the atmosphere than is currently released
by human activity. In an article appearing in the journal Science, the
researchers assumed a 10 to 20 percent loss rate due to leakage. Because
molecular hydrogen freely moves up and mixes with stratospheric air, the
result would be the creation of additional water at high altitudes and an
increased dampening of the stratosphere, and, indirectly, destruction of
ozone.

In this respect, hydrogen leakage would be similar to chlorofluorocarbons
(CFCs) -- once the standard substances used for air conditioning and
refrigeration. They were intended to be contained within their devices,
but in practice CFCs leaked into the atmosphere and attacked the ozone
layer. CFCs have been widely replaced by alternative substances and are
set for a complete phase out under an international agreement.

However, the authors of the report say uncertainty remains about the
effects of hydrogen on the atmosphere because scientists still have a
limited understanding of the hydrogen cycle. They also note that, unlike
the case with CFCs and other atmospheric pollutants like carbon dioxide,
the current situation is unique in that society has the opportunity to
understand the potential environmental impact well ahead of the growth of
a hydrogen economy.

Following is the text of the press release:

(begin text)

California Institute of Technology
June 12, 2003

Hydrogen economy might impact Earth's stratosphere, study shows

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