 |
| "As alterações climáticas fazem com que ocorram fenómenos cada vez mais extremos e cada vez mais repetitivos. O clima está a evoluir, ou seja o equilíbrio das massas dinâmicas da atmosfera e do oceano estão em transformação. Se puxarmos a corda de um lado, a Natureza encarrega-se de encontrar o equilíbrio do outro."LUÍS QUARESMA DOS SANTOS |
Que ondas são estas?
por Ricardo J. Rodrigues Fotografia de Orlando
Almeida/Global Imagens
in Notícias Magazine . / DN online
As ondas que têm assolado a costa portuguesa não são
propriamente altas, são sobretudo compridas. Resultam de uma conjugação entre
disparidades térmicas, ventos fortes e empilhamento de água junto à terra. Luís
Quaresma Santos, oceanógrafo do Instituto Hidrográfico e tenente da Marinha,
explica o fenómeno por detrás das imagens impressionantes que todos vimos nas
últimas semanas.
Este início de ano está a ser marcado pela ondulação gigante
na costa portuguesa. O mar está mais perigoso?
A onda gigante da Nazaré, que foi surfada pelo Gareth
McNamara, é muito maior em altura do que estas ondas. O que torna estas ondas
perigosas é o seu comprimento. As ondas podem durar seis segundos e o que foi
extraordinário neste evento foi a chegada de ondas que duravam 22 ou 23
segundos, um comprimento de onda enorme.
O que é que criou uma agitação marítima tão excecional?
Tivemos durante vários dias ventos muito fortes a atuar em
toda a superfície do oceano. Os ventos começaram na costa Leste dos Estados
Unidos e o efeito de rotação da terra fez com que essa tempestade se tenha
movimentado por toda a bacia oceânica em direção à Europa. Como a tempestade
começa a gerar ondas e as ondas começam a ser empurradas para um sítio longe de
onde elas tinham sido formadas, a tempestade propagou-se em cima da agitação
que já existia, fazendo-a aumentar.
Estamos a falar de horas?
Não, estamos a falar de dias. O que acontece é que, com a
frente polar que chegou à América do Norte, criou-se uma depressão atmosférica
e um contraste de pressões que provocou ventos muito fortes e constantes. Esses
ventos foram fustigando a superfície da água, ampliando a ondulação. A
tempestade foi alastrando para oriente e, a determinada altura, já ocupava todo
o Atlântico Norte.
Resumindo: a vaga de frio criou vento nos oceanos e a
rotação da terra empurrou esses ventos para a Europa.
Exatamente. Este ar frio era molecularmente menos denso e
criou uma problema de pressão térmica sobre a superfície do mar. Todo o planeta
recebe energia solar e o mar tem uma capacidade maior de armazenar o calor do
que o ar. É por isso que os oceanos não congelam. Se o ar está mais frio do que
a água, o calor vai passar do oceano para a atmosfera. Quando isso acontece, as
partículas vão pouco a pouco tornado-se menos densas e o ar sobe, criando os
tais ventos. Neste caso, o contraste entre a temperatura do ar e da água foi
tão extremo que criou uma grande tempestade oceânica. E consequentemente uma
agitação marítima excecional.
Mas nos últimos anos houve Invernos também rigorosos e não
se notou tanto este fenómeno de ondulação.
O problema desta vez é que o frio chegou ao Golfo do México,
que é um dos grandes reservatórios de calor do Atlântico Norte. Por causa da
depressão criada pela temperatura, a água teve de escapar do golfo para Norte.
O movimento de rotação da terra, como já vimos, foi fazendo o excesso de água
que o oceano recebeu avançar na nossa direção, sempre fustigada pelo vento.
Quando encontrou um obstáculo, a água começou a empilhar-se na costa até entrar
terra adentro. Os ventos, então, fizeram essa água chegar-nos sob a forma de
ondas de grande dimensão.
É provável que estes episódios de ondulação perigosa se
repitam nos próprios anos?
As alterações climáticas fazem com que ocorram fenómenos
cada vez mais extremos e cada vez mais repetitivos. O clima está a evoluir, ou
seja o equilíbrio das massas dinâmicas da atmosfera e do oceano estão em
transformação. Se puxarmos a corda de um lado, a Natureza encarrega-se de
encontrar o equilíbrio do outro.
E estamos preparados para fenómenos destes?
Temos uma rede de monitorização oceânica que está em
permanência a observar o vento, a pressão e a agitação marítima. E o Instituto
Hidrográfico está em permanente contacto com o Instituto do Mar e da Atmosfera.
Quando há situações de emergência, a Proteção Civil declara o nível de
perigosidade para pessoas e bens.
Uma agitação marítima destas dimensões há de ter um impacto
fortíssimo em termos de erosão. Vamos ficar sem praias, com o passar do tempo?
No Inverno o mar rouba sempre imensa areia às praias, que é
reposta no Verão por causa dos rios. Os cursos de água doce transportam
sedimentos que vão repor o equilíbrio. O problema é que as barragens
interromperam esta ordem natural. E também o transbordo de águas. Espanha está
a desviar águas reduzindo os caudais dos rios, e impedindo a reposição da
areia. O problema da erosão não vem tanto destes fenómenos naturais, vem muito
mais da ação humana.
Estas ondas perigosas têm alguma coisa a ver com um tsunami?
O tsunami tem uma origem diferente, que é a destabilização
da crosta. Mas, da mesma forma, cria uma depressão que provoca uma onda de
grandes dimensões. Agora, se neste caso estamos a falar de ondas que duram, no
máximo, 25 segundos, quando falamos de um tsunami falamos de um transbordo de
água em terra que dura dois minutos e meio. O impacto é completamente
diferente.
A onda é então uma libertação de energia do mar, por causa
das variações de pressão?
Sempre. Mas não se pense que as ondas se revelam apenas à
superfície, elas também se propagam no interior do oceano, com a
particularidade de serem ondas muito maiores, porque a densidade do mar é muito
maior do que à superfície. Dentro do mar há ondas que alcançam oitenta metros
de altura, por exemplo. E podem rebentam no interior do próprio oceano, sem
nunca atingir a costa. Não as vemos, mas elas estão lá.
Mas se temos atividade sísmica no Atlântico, nomeadamente
nos Açores, porque é que a nossa costa, que é aberta ao oceano, não é fustigada
por um grau maior de agitação marítima?
Precisamente por causa dos Açores, ou antes, do anticiclone
dos Açores, que é um centro de altas pressões que desvia a corrente marítima
para Norte. É isso que explica o nosso clima, a nossa exposição excecional ao
sol e uma baixa agitação marítima, sobretudo no verão. No Inverno, o
anticiclone enfraquece e, no caso do que vivemos nestes últimos dias em
Portugal, desaparece por completo. Países como a Irlanda estão habituados a
este grau de agitação marítima porque não beneficiam do centro de altas
pressões dos Açores.
Então porque é que uma tempestade destas dimensões não se
sentiu da mesma forma em terra como no mar? Se o Hércules, que nos Estados
Unidos manifestou-se através de um frio glaciar, atravessou todo o Atlântico,
não deveríamos ter sofrido uma vaga de frio semelhante?
A tempestade Hércules atravessou o Atlântico e o oceano foi
aquecendo o ar ao longo do processo. No dia 6 de janeiro, o nível do mar já
tinha subido meio metro, porque a tempestade e a diferença de pressão
provocaram um empilhamento de água na nossa costa. Se subiu meio metro, uma
onda que antes rebentava na praia, vai agora rebentar na dura. Quando a maré
subiu, entre o meio dia e as seis da tarde, formaram-se ondas grandes e
compridas e transbordaram de forma significativa para dentro de terra.
Pode ter sido uma onda destas que apanhou desprevenido, em
dezembro, um grupo de universitários no Meco?
Não quero especular sobre o caso, até porque ele está a ser
investigado. Mas sabemos que as ondas não têm sincronia, vêm umas maiores e
outras mais curtas. Em média, a cada sete ondas há uma vaga que transporta
maior volume de água. E não só o transbordo é maior como o refluxo também é
mais acentuado. Se as pessoas estiverem próximas da água podem ser levadas pelo
mar. Em Portugal, e nomeadamente no Meco, são frequentes as correntes de
retorno, conhecidas popularmente por agueiros. A água que dá à costa entra num
corredor de refluxo para mar alto. Ser apanhado numa situação destas
desprevenido, ainda mais usando roupa de Inverno, pode ser fatal.
LUÍS QUARESMA DOS SANTOS
Tem 36 anos e é um dos principais oceanógrafos do país.
Doutorado em Oceanografia Física pela universidade de Brest, em França, é
primeiro tenente da Marinha Portuguesa e investigador no Instituto
Hidrográfico, principal centro de investigação da Armada. O seu trabalho incide
sobre o estudo, a observação e previsão de marés, correntes oceânicas e
agitação marítima.
Cheias históricas do rio Tamisa forçam mega operação
de emergência no Reino Unido
RITA SIZA 10/02/2014 – in Público
Cidade de Londres não está ameaçada, mas a Protecção Civil
emitiu 16 alertas de cheias severas com riscos para a vida.
Numa operação de larga escala, dezenas de localidades
inundadas por cheias históricas do rio Tamisa estão a ser evacuadas pelas
autoridades britânicas, que lutam contra o tempo para retirar os habitantes das
áreas onde, de acordo com a protecção civil, podem correr “perigo de vida”.
Em vários pontos de medição, o caudal do Tamisa já
ultrapassou o nível que constituía o máximo histórico, e segundo as projecções,
o caudal continuará a aumentar nas próximas 24 horas por causa das chuvas
torrenciais que afectam o Sudoeste de Inglaterra. De acordo com os registos, o
mês de Janeiro foi o mais chuvoso desde 1776.
A Protecção Civil emitiu 14 alertas de cheias “severas” nas
regiões do Berkshire e Surrey, e outros dois para o Somerset – que tem estradas
intransitáveis desde Dezembro e terras de cultivo inundadas há um mês. A área
ameaçada já incluía a zona metropolitana de Londres: Windsor, a cerca de 30
quilómetros da capital, corre um sério risco de inundação. No entanto, a
barreira de protecção que envolve Londres desde 1982 (uma série de “portões”
metálicos que travam o fluxo do rio) estava a funcionar para proteger a cidade.
Mas a Oeste e a Sul da capital mantinham-se em vigor 133
alertas (menos graves) de cheia e 215 avisos para a possibilidade de inundação,
com a recomendação de que as populações tomem providências para proteger os
seus bens.
De acordo com a agência ambiental do Reino Unido, uma das
localidades mais afectadas, a vila de Datchet, encontra-se totalmente inundada.
Mas “centenas de outras comunidades” no curso do Tamisa estão “seriamente
ameaçadas” por causa da subida do nível das águas. “O risco de cheia dos rios
Tamisa, Severn [o rio mais longo do Reino Unido] e Wye permanece muito elevado
ao longo da semana”, alertou a Protecção Civil.
Os prejuízos das cheias são avultadíssimos, mas por enquanto
é difícil calcular os custos da perda da produção agrícola e da destruição de
edifícios – pelo menos 8000 casas foram inundadas – e infraestruturas. Um
analista de seguros da Deloitte em Londres disse à Bloomberg que se “a
acumulação de queixas relacionadas com fenómenos extremos se prolongar até ao
fim de Fevereiro, o sector poderá enfrentar uma factura de cerca de 500 milhões
de libras [cerca de 600 milhões de euros]”.
Com as linhas de comboio parcialmente submersas, a
circulação ferroviária em várias linhas do Sul e Sudoeste foi suspensa até
quinta-feira. A Network Rail, que gere o sistema, reportou problemas graves em
cerca de 500 pontos da rede – a média de incidentes nesta época do ano não
chega sequer às duas dezenas. Várias estradas também foram cortadas, bem como a
passagem em pontes.
O Governo convocou o Exército nacional para colaborar nas
operações de salvamento necessárias mas, principalmente, trabalhar na
edificação de barreiras anti-cheia, que nalguns casos estavam a revelar-se
incapazes de suster o avanço das águas. Os habitantes comparam a paisagem a um
“cenário de filme de terror”, com o rio a galgar as margens e destruir as
paredes erguidas com sacos de areia assim que estas ficam prontas.
Debaixo de crítica da oposição pela aparente falta de
preparação para responder à intempérie, o Governo garantiu que “todos os
esforços estão a ser feitos” para garantir a protecção e segurança das
populações das áreas afectadas pelas cheias.
Numa curta declaração, na costa de Portland, o
primeiro-ministro, David Cameron, sublinhou que o seu “único interesse é ter a
certeza que tudo o que pode ser feito está a ser feito – e continuará a ser
feito – para ajudar as pessoas que estão a viver tempos difíceis.
Disponibilizamos o dinheiro e os recursos necessários para atender à situação”.
Why has it rained so much in the UK – and is it
climate change?
Report highlights high
pressure over patch of Pacific Ocean and phenomenon known as quasi-biennial
oscillation
Nicola Davis
The Guardian, Tuesday 11 February 2014 / http://www.theguardian.com/environment/2014/feb/11/why-has-it-rained-so-much-climate-change?CMP=fb_gu
Brits may be obsessed with the weather, but having endured
more than two months of persistent heavy rain, powerful waves and severe
storms, this is no longer the topic of small talk. January in the south of
England was the wettest since record-keeping began more than 100 years ago and
across the country the drastic conditions have devastated homes, thrown lives
into confusion and fuelled a political bunfight. The Met Office and the Centre
for Ecology and Hydrology have released a report shedding light on the endless
downpours and have begun to explore whether climate change is a contributing
factor.
Why has the weather been so wet?
Dame Julia Slingo, the Met Office's chief scientist said on
Sunday that the UK had seen the "most exceptional period of rainfall in
248 years".
The report reveals that while downpours and storms have not
been out of the ordinary, their frequency has been.
"Each one of these individual events has not been
particular outstanding, they've been broadly along the lines of what we would
expect for a typical winter storm in the UK," said Simon Parry from the
CEH and co-author of the report. "What's been notable about it, and
different from what we've seen in the past, is the persistence."
That, according to Professor Adam Scaife from the Met Office
and another author of the report, is down to a series of deep low pressure
systems linked to the jet stream – wind that blows from west to east across the
Atlantic. "When the jet stream is strong then the storms are strong,"
said Scaife.
"It's normally stronger in winter than it is in summer
but this year it has been exceptionally strong and that is absolutely bound to
the storminess because the jet stream steers the storms but it also feeds off
them."
Why the abnormally strong jet stream?
The report highlights two key factors the authors believe
have contributed to the effect.
The first is a persistent high pressure system lurking over
a patch of the Pacific Ocean, off the west coast of North America. This high
pressure system is sending a chill across the US.
"The air tends to rotate in a clockwise fashion around
the high pressure system," said Scaife. "That is going to drag the
air from up near the Arctic down over North America."
As a result, Canada and North America have been held in an
icy grip for weeks. And further east, as the cold air from North America meets
the warm air from the tropics, a large temperature gradient – the rate at which
temperature changes with distance – is created.
"The storms feed off that temperature gradient – the
stronger that gradient the more conducive it is to growing storms," said
Scaife. "As the storms grow they also flux momentum into the jet
stream," he added, "and of course sitting downstream at the end of
that path is us."
Another effect in the report is the quasi-biennial
oscillation (QBO). This is where a band of fast-moving winds that blow around
the equator change direction.
"You see roughly every 14 months the winds reverse and
instead of blowing form the east towards the west they flip and the blow from
west to east," said Scaife.
The last time this happened was in early 2013. And while the
equator is hundreds of miles away, the effects of QBO can be felt closer to
home.
"When the QBO is blowing from the west then this also
strengthens the jet stream over the Atlantic and increases the amount of
storminess," said Scaife. And with these winds in a strong westerly phase
this winter, they too may have contributed to the relentlessly violent weather.
Is this pattern likely to be repeated in future winters?
It is hard to say at this stage. "Probably next year
the QBO will have flipped but there are other factors that drive the jet stream
so its not possible at this range to say whether next winter will be the
same," says Scaife.
Is climate change ultimately the cause?
It is not possible to link the current floods definitively
to climate change. "In terms of the number of storms there is scant
evidence that has been increasing due to climate change so far," said
Scaife. "[But] we do expect that winter rainfall is likely to increase in
the future." This is in part down to a warming planet. "As the air
warms it can hold more water."
 |
| "People have good reason to believe that that was a fairly cynical exercise and that much of the party remains unconvinced of the need to have a coherent environmental policy," Browne said. |
Severe floods 'threaten food security', say farmers
and environmental groups
Government accused of failing
to address effects of climate change on coastal and rural areas
Jamie Doward, Toby Helm, Damian Carrington and Robin McKie
The Observer, Saturday 8 February 2014 / http://www.theguardian.com/environment/2014/feb/08/severe-floods-threaten-food-security-climate-change
Severe flooding threatens to undermine the country's food
security, according to farmers and environmental groups, who today accuse the government
of failing to address the effects of climate change on coastal and rural areas.
As gales swept southern and western parts of the UK, with
already drenched counties bearing the brunt of the storms, it has emerged that
parliament's select committee on the environment warned in a report last year
that "the current model for allocating flood defence funding is biased
towards protecting property, which means that funding is largely allocated to
urban areas. Defra's [the Department of the Environment's] failure to protect
rural areas poses a long-term risk to the security of UK food production, as a
high proportion of the most valuable agricultural land is at risk of
flooding."
"We need a response from government that recognises the
importance for our long-term food security of safeguarding high-quality
farmland," said Neil Sinden of the Campaign to Protect Rural England.
"We need to view the countryside as more than a place for building, and
value it for the food it provides."
Defra has estimated that 35,000 hectares of
high-quality horticultural and arable land will be flooded at least once every
three years by the 2020s. This could rise to around 130,000 hectares
by the 2080s if there is no change to current flood defence provision.
Peter Kendall, chairman of the National Farmers Union, which
has produced evidence showing that 58% of England's most productive farmland
lies within a floodplain, said the floods were a wake-up call for a country
that has "believed for too long that producing food wasn't a big
issue".
"We are seeing more of these intense extreme weather
events," Kendall said. "Climate change does now really challenge
mankind's ability to feed itself."
He said much of the flooding was down to "almost a
deliberate policy of neglect of the watercourses" that had seen the
Environment Agency "putting birds first and people second", a
reference to the agency's attempts to encourage more wetland areas in the UK to
promote biodiversity.
His comments were the latest salvo fired at the agency's chairman,
Lord Smith, who was defended robustly by wildlife charities. In a letter in the
Observer, the heads of the RSPB, the Wildfowl and Wetland Trusts, the Wildlife
Trusts and the Angling Trust, said: "Ultimately, it is governments that
have set the policies that have hamstrung flood planning in some vulnerable
areas: allowing homes to be built and failing to make both homes and farmland
more resilient to floods. Cuts to the Environment Agency merely risk reducing
it from a flood-management body to an emergency response service and making
future floods even more damaging."
Whistleblowers within the agency told the Observer that
frontline flood staff were being cut, despite Smith's pledges that reducing the
agency's emergency response was a "red line" that could not be
crossed.
"People need to be aware that some of the frontline
staff are taking a big hit, particularly when we are facing some of the worst
flooding ever seen in southern England," said one EA source. He said that,
at the same time that frontline staff were being put onto 24/7 duty rotas,
managers were being asked to cut staff by 13% across all regions. "This
salami slicing approach is entirely wrong," he said.
"This government is steadily dismantling the nation's
ability to tackle flooding and prepare for climate change," said Friends
of the Earth's Guy Shrubsole.
An Environment Agency spokesman said: "The planned
reductions in posts will not affect the Environment Agency's ability to respond
to flooding incidents."
The government's response to the floods is threatening to
damage the Tory brand in rural areas. Jeremy Browne, the Liberal Democrat MP
for Taunton Deane, said that the Conservatives had left themselves open to
criticism, having rebranded themselves as a "green" party, only to
lose enthusiasm after a couple of years in office.
"People have good reason to believe that that was a
fairly cynical exercise and that much of the party remains unconvinced of the
need to have a coherent environmental policy," Browne said.
Global warming pause is a mirage: the science is clear
and the threat real
 |
| Global warming pause is a mirage: the science is clear and the threat real |
Global warming 'pause' due to unusual trade winds in
Pacific ocean, study finds
Study shows sharply
accelerating trade winds have buried surface heat underwater, reducing heat
flowing into atmosphere
Oliver Milman / The Guardian, Monday 10 February 2014 / http://www.theguardian.com/environment/2014/feb/09/global-warming-pause-trade-winds-pacific-ocean-study
The contentious "pause" in global warming over the
past decade is largely due to unusually strong trade winds in the Pacific ocean
that have buried surface heat deep underwater, new research has found.
A joint Australian and US study analysed why the rise in the
Earth's global average surface temperature has slowed since 2001, after rapidly
increasing from the 1970s.
The research shows that sharply accelerating trade winds in
central and eastern areas of the Pacific have driven warm surface water to the
ocean's depths, reducing the amount of heat that flows into the atmosphere.
In turn, the lowering of sea surface temperatures in the
Pacific triggers further cooling in other regions.
The study, which is published in the journal Nature Climate
Change, calculated the net cooling effect on global average surface
temperatures as between 0.1C
and 0.2C, accounting for much of the hiatus in surface warming. The study's
authors said there has been a 0.2C
gap between models used to predict warming and actual observed warming since
2001.
The findings should provide fresh certainty about the
reasons behind the warming hiatus, which has been claimed by critics of
mainstream climate science as evidence that the models are flawed and
predictions of rising temperatures have been exaggerated.
The UN's Intergovernmental Panel on Climate Change (IPCC)
addressed the warming pause issue in its 2013 climate report, pointing out that
the Earth is going through a solar minimum and that more than 90% of the
world's extra heat is being soaked up by the oceans, rather than lingering on
the surface.
Matthew England, a climate scientist at the University of
New South Wales in Sydney, and leader of the research, said that while the
solar minimum and aerosol particles have contributed to the slowdown, strong
trade winds are the significant factor.
"Temperature models have an envelope of uncertainty but
it is clear that the last decade has seen a much flatter temperature change
compared to the 1980s and 1990s, when the increase was rapid," he said.
"We found that the wind acceleration has been strong
enough in the past 20 years to pump a lot of the heat into the ocean. Winds
accelerated in this period more than at any time in the past century; it really
is unprecedented and the models haven't captured it all."
The acceleration of Pacific trade winds has been twice as
strong in the past 20 years compared with the prior 80 years, cooling the east
Pacific and propagating the trend to other parts of the world.
The study suggests the warming hiatus could continue for
much of the present decade if the trade winds continue; however, should the
winds return to their long-term average speeds, rapid warming will resume.
"Even if the winds accelerate even further, sooner or
later the impact of greenhouse gases will overwhelm the effect," England
said. "And if the winds relax, the heat will come out quickly. As we go
through the 21st century, we are less and less likely to have a cooler decade.
Greenhouse gases will certainly win out in the end."
England said it was unclear what has caused the increase in
Pacific trade winds, although warming in the Indian Ocean has been cited as a
potential trigger.
Dr Steve Rintoul, research team leader at CSIRO Marine and
Atmospheric Research, said the research shows that pauses in the rate of global
warming are to be expected.
"The oceans have continued to warm unabated, even
during the recent hiatus in warming of surface temperature," he said.
"Natural variations of the climate system also mean
that climate trends estimated over a short period are unlikely to reflect
long-term changes. A decade or two of slower or faster warming does not tell us
anything about long-term climate change."
Richard Allan, professor of climate science at the
University of Reading, said it is likely the current warming slowdown is only a
temporary reprieve from brisk increases in global temperatures.
"This new research suggests that when the trade winds
weaken again, the planet can expect rapid warming of the surface to resume, as
greenhouse gas concentrations continue to rise," he said.
"We don't know what is causing these unprecedented
changes, but the implications could be substantial."
Only 1% of the heat trapped
by greenhouse gases warms the air, making the pause claimed by IPCC critics an
idiotic sideshow
Posted by
Damian Carrington
Friday 27 September 2013 15.14 BST
theguardian.com / http://www.theguardian.com/environment/damian-carrington-blog/2013/sep/27/global-warming-pause-mirage-ipcc
The landmark new report from the Intergovernmental Panel on
Climate Change (IPCC) is crystal clear: human action is warming the planet and
we're heading for big trouble if carbon emissions are not slashed. As Prof Tim
Palmer, at the University of Oxford put it: "The report is further
reinforcement that there is an unequivocal risk of dangerous climate
change."
Yet before the ink is even dry critics are trying to obscure
this stark message behind a mirage: the supposed halt in global warming over
the last 15 years. This willful idiocy is based on the fact that air
temperatures at the Earth's surface have more or less plateaued since the
record hot year in 1998.
What critics choose to ignore is that of all the extra heat
being trapped by our greenhouse gas emissions - equivalent to four Hiroshima
nuclear bombs every second - just 1% ends up warming the air. By choosing to
focus on air temperatures critics are ignoring 99% of the problem.
Are scientists certain that global warming has continued
unabated over the last 15 years? Yes. "The best satellite data we have
shows that there is still more energy going into the climate system than is
going out, because of greenhouse gases in the atmosphere," said Ed Hawkins,
at the University of Reading. Another Reading scientist, William Collins, said:
"The climate has warmed over the last 10 years, the models are not wrong
on the total heat being added."
So where is all the heat going? About 93% goes into the
oceans, much of which were largely unmonitored until the 2000s, 3% into land
and 3% into melting ice.
Undue focus on the air temperature plateau is cretinous for
several more reasons. First, unlike weather, climate is a long term phenomenon
and can only truly be assessed over at least 30 years. While the long term
warming trend is clear, scientists have long known that air temperatures do not
rise smoothly year-on-year in the complex and chaotic climate system and that
decade-long ups and downs are part of natural variability.
"The very first climate models built in the 1990s
showed this kind of variability, so we have known about this for a long
time," said Hawkins. John Shepherd, at the UK National Oceanography
Centre, said: "We should prepare for a bumpy ride, as that is what we have
had in the past and that is what we will have in the future."
Second, if air temperatures have not risen quickly in the
last 15 years, other clear indicators of climate change have worsened more
quickly than expected, including the rapid loss of Arctic ice and sea level
rise. Critics cannot cherry pick their indicators and remain credible.
Thirdly, many scientists anticipated the so-called
"pause": it is not some shock undermining the whole edifice of
climate science. A natural and periodic ocean current phenomenon called El Niño
peaked in 1998, pumping heat into the air, but has been increasingly in
abeyance since. Furthermore, the solar cycle peaked in 2002 and the reached its
minimum in 2009, meaning a little less heat beaming down to Earth, and a number
of volcanic eruptions have blocked out some sunlight in that time.
So the pause in air temperatures can be well explained and,
while work remains to be done determining the exact relative importance of
ocean heating, El Niño, solar cycles and volcanoes, we are still only talking
about 1% of global warming. Prof David Mackay, the UK's government's chief
energy and climate change adviser, is clear: "It is not a terrible
mystery."
Another mirage being conjured up is the debate about climate
"sensitivity", i.e. how much air temperatures rise for a given rise
in carbon dioxide in the atmosphere.
Some scientists have suggested the climate is less sensitive
than thought and there is a genuine debate about this. But the differences
being discussed are essentially irrelevant. Thomas Stocker, one to the two
scientists who oversaw the IPCC report, gave this criticism short shrift: The
slightly lower sensitivity being discussed would give humanity only a "few
years" longer to tackle climate change, he said: "It is not really a
relevant point when it comes to the relevant reductions in CO2 emissions needed
to keep temperature rise under 2C ."
The estimates of climate sensitivity come out of the complex
computers models used to project warming into the future. The IPCC states that
the models, built on the basic laws of physics, now accurately represent a
great many of the important climate phenomena. "If you are saying the
models are flawed, you are saying the laws of physics are flawed," said
Tim Palmer, at the University of Oxford.
Be in no doubt, climate change is real and dangerous. In
fact, the new IPCC report, written in consensus by the world's climate experts
and signed off in unison by the world's governments, may well be too timid.
That is because it is a scientific document in which the confidence in climate
knowledge and predictions are assessed. It is not a risk assessment.
"If there is a 10% chance of an aircraft crashing, you
would not board it, but the IPCC classes that as very unlikely," said Ted
Shepherd, at the University of Reading. The IPPC concludes there is a 50-50
chance that global temperatures will exceed 4C this century if carbon emissions are not
curbed. Such a rise would have catastrophic consequences. So if you are still
feeling confused about all this complex science, it all boils down to this: how
lucky do you feel?
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