Mudança  Climática Global
Autor: Ciências do Ambiente na Engenharia | Publicado: 2011-10-24T21:40:00-03:00

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Há cerca de 200 anos, a Revolução Industrial inaugurou uma&nbsp; era em que os humanos dependem de combustíveis fósseis para fazer funcionar as máquinas usadas na indústria e no dia-a-dia. Desde então, o consumo das fontes de dióxido de carbono aumentou continuadamente, principalmente por causa da atividade industrial e do desmatamento. A população também só aumentou. Uma parte do dióxido de carbono liberado na atmosfera é absorvido pelas plantas ou dissolvido nos oceanos: as florestas e os mares funcionam como os “ralos” de carbono. Mas a atividade humana vem emitindo dióxido de carbono mais rápido do que dá para absorver naturalmente. 
  
     
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Outros gases do efeito estufa também têm seus níveis elevados: a quantidade de metano mais do que dobrou e o&nbsp;óxido nítroso&nbsp;aumentou mais de 17%. Além desses aumentos de concentração, os humanos ainda acrescentaram à atmosfera gases de efeito estufa que não existiam até o século XX, como os clorofluorcarbonos (CFCs). Nós estamos mudando a atmosfera mais rápido do que nunca.


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 <![endif]-->  Atividade humana aumenta emissão de gases de efeito estufa
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Bem como aumentos de temperatura, muitos outros aspectos do clima vêm mudando. Alguns países tiveram chuvas mais fortes, enquanto outros sofreram secas. Há pouca evidência de mudança de regime de chuvas no Brasil, embora um leve aumento no volume tenha ocorrido no último século. Um dado que reforça essa observação é que na bacia do Rio Paraná, que cobre um milhão de quilômetros quadrados e inclui São Paulo e Brasília, foi percebido um aumento de 15% no fluxo de água nas décadas mais recentes.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp; &nbsp; &nbsp; &nbsp; Em muitas partes do mundo, houve uma redução do tempo de congelamento de lagos e rios e um aumento de ondas de calor. Geleiras do topo das montanhas encolheram, a espessura do gelo do Ártico no final do verão foi reduzida em 40% e os níveis do mar aumentaram entre 10 e 20 cm. Essas mudanças condizem com as mudanças climáticas e os cientistas acreditam que vão continuar sendo observadas no futuro, mas não é possível dizer com certeza que todas elas acontecem por causa do aumento do efeito estufa.
Textos de apoio:
http://univesp.tv.br/site/programas/mudanca-climatica-global
http://www.invivo.fiocruz.br/cgi/cgilua.exe/sys/start.htm?infoid=924&amp;sid=9
Grupo: Juliana Ribeiro, Gilberto Pinheiro, Alan Pinheiro e Jonas Dantas.