Climate models are not only used to look at how climate might change, they’re also used to figure out WHY it’s changing. When models are run with only natural influences from the sun and volcanic eruptions, they say that during the latter half of the 20th century, we would have expected little change from normal conditions (the blue line). Only the addition of human emissions (greenhouse gases, sulfates, and ozone) produce the model results in red that most closely reproduce the black line of actual observations. So, although they aren’t perfect, climate models can reproduce many of the larger features of climate change in Earth’s distant past, and they replicate the pattern of warming in the last 100+ years. This gives us confidence that they correctly identify that the warming is due to man’s activities, and that projections of future warming are realistic.

Bizi endişelendirmeli mi? Global average temperatures are expected to increase by about 2-13°F (1-7°C) by the end of the century. That may not sound like a lot, so what’s the big deal? The problem is that small changes in global average temperature can lead to really large changes in the environment. Let’s look at some of the expected changes.

Deniz suyu seviyesi tahminleri: 60 cm.: A.B.D.’de 26,000 km2 alan sular altında 90 cm: Miami sular altında Aşınma, sulak alan ve tatlı su kaynaklarının kaybı Dünya nüfusunun yarısından fazlası kıyı alanlarında yaşamakta. The oceans will continue their rise in the coming century. The IPCC’s best estimates range from a few inches to a few feet by 2100. If the rise is 2 feet, the US could lose 10,000 square miles, If they rise three, they will inundate Miami and most of coastal Florida. Sea-level rise also increases coastal erosion and the loss of coastal wetlands, and saltwater spoils freshwater drinking supplies. Coastal populations become even more vulnerable to storm surge and flooding. Considering that half of the world’s population lives near coasts, sea-level rise is a serious concern. The big unknown in all this is how much the planet’s ice sheets will melt.

Ancak aşırı avcılık ve küresel ısınmanın da etkisiyle son yıllarda bu göçte bir hızlanma olması dikkat çekici. Öyleki Mersin Körfezinde bazı ağlarda yakanan balıkların  %80’inden fazlasını yabancı türler oluşturuyor. ODTÜ Deniz Bilimleri Enstitüsü, Mersin [Image 1] A warming planet means continuing changes in its ecosystems. As the oceans absorb more carbon dioxide, the chemistry of the ocean changes, putting many sea creatures at risk. The IPCC projects that by 2100 the pH of the ocean will drop to its lowest point in at least 20 million years. [click, Image 2] As temperatures get milder, mosquitoes, ticks, rodents, and other disease carriers will expand their range, particularly in developing countries. Here in the U.S., dengue hemorrhagic fever, a tropical, mosquito-borne disease, hit for the first time in modern times in 2005 in the Lower Rio Grande Valley. [click, Image 3] Warmer temperatures will also mean less snow overall at certain latitudes because more will fall as rain, and the snow that does fall will melt faster. This affects people living in areas that depend on snow-fed reservoirs for water. [click, Image 4] The IPCC projects increases of 5-20% in crop yields in the first decades of this century. but the crops will be more prone to failure if climate variability increases and precipitation becomes less dependable. And ironically, with higher temperatures comes an increased potential for killing freezes. This is because plants start growing earlier, making them more vulnerable to sudden spring-time cold spells.

Türkiye’de durum Son 50-60 yıllık dönemde dağ buzullarında yılda yaklaşık 10 metrelik geri çekilme gözlenmiştir [Sarıkaya, 2011]. • Son 40 yıllık dönemde karla beslenen nehirlerde tepe akımları bir hafta mertebesinde erkene kaymıştır [Yücel, 2013]. • Türkiye’yi çevreleyen denizlerde deniz seviyesi yükselmektedir [Demir, 2005]. Demir, Coşkun., Yıldız, Hasan., Cingöz, Ayhan., ve Simav, Mehmet. 2005. Türkiye Kıyılarında Uzun Dönemli Deniz Seviyesi Değişimleri, 13 sayfa, V. Ulusal Kıyı Mühendisliği Sem- pozyumu, 5-7 Mayıs, Bodrum. IPCC. 2013. “Working Group I Contribution to the IPCC Fifth Assessment Report.” Climate Change 2013: The Physical Scien- ce Basis, Summary for Policymakers. Geneva: IPCC Secretariat. http://www.climatechange2013.org Sarıkaya, Mehmet Akif. 2011. “Türkiye’nin güncel buzulları.” Fiziki Coğrafya Araştırmaları: Sistematik ve Bölgesel (içinde), İstanbul: Türk Coğrafya Kurumu Yayınları, 6: 527-544. İsmail, Yücel., Güventürk, Abdülkadir., ve Şen, Ömer Lütfi. 2013. “Climate change impacts on snowmelt runoff for mountainous regions of eastern Turkey”, Journal of Hydrology

Bilim insanları ne kadar emin? Nothing in science is 100% certain There are no laboratory experiments that can tell us what the future will be—the planet IS the test tube [click to reveal bullets] What don’t we know? Is there some climate process we don’t know about? So far, research over the years has strengthened the conclusion that humans are adversely influencing climate, but scientific knowledge is still evolving We don’t know how things might change in the future, such as Will alternative energy sources become widely available? How soon? Will some yet-to-be-discovered technology be able to clean CO2 out of the air? How will changing economics, global population, and political processes affect our ability to tackle the problem?

The IPCC (Hükümetler Arası İklim Paneli) [Image 1] The International Panel on Climate Change, the group that produces the main reports on climate change, is a scientific intergovernmental body set up by the World Meteorological Organization (WMO) and by the United Nations Environment Programme in 1988. [click, Image 2] The IPCC process involves hundreds of scientists from about 140 countries, a variety of fields, and a range of views. Their function is to assess the latest peer-reviewed literature, [click Image 3] compare different computer model results from various sources, and to achieve consensus about where the weight of the evidence points and where uncertainties lie. And

RAKAMLARLA COP21 2°C - COP21’in küresel sıcaklık artışı hedefi 40.000 - Toplam katılımcı sayısı 196 - Katılan tarafların sayısı 3.000 COP21’de görev yapacak kişi sayısı 11.000 Zirvede görev yapacak polis sayısı 0 - Şimdiye kadar iklim değişikliği konusunda gerçekten yasal olarak bağlayıcı ve küresel anlaşma sayısı 170 milyon Euro - COP21’e harcanacak toplam bütçe % 30 - Küresel ısınma bu seviyelerde devam ederse, bu yüzyıl bitmeden kaybedilecek biyoçeşitlilik oranı 1 metre - Mevcut yolda devam edersek, 2100’e kadar su seviyesinin yükselebileceği rakam Also, there are scientists who disagree with the IPCC—they believe the conclusions are too conservative and that things will be worse than projected. There is some evidence to support their views. Arctic sea ice is melting much faster than scientists predicted. Also, actual fossil fuel emissions in recent years have exceeded all but the highest IPCC projections, growing four times faster than in the 1990s. Some argue that the IPCC near-future assumptions about global energy use are too optimistic. A recent study also concludes that the IPCC estimates were too rosy with regard to how quickly developing countries will be able to afford technologies to reduce greenhouse gas emissions. Scientists in this camp also say sea levels may rise far more than we anticipate because our calculations aren’t taking into account the unexpectedly large melting of the Greenland and Antarctic Ice Sheets.

COP 21 Kararları Anlaşmaya katılan ülkelerin küresel sıcaklık artışını yüzyılın sonuna kadar 2 derecenin altında tutmak için çaba sarf etmesi gerekiyor. Sıcaklık artışının 2 derece ile sınırlandırılması, karbon emisyonunun yüzde 40 ila 70 seviyesinde azaltılması anlamına geliyor. Ülkeler iklim zirvesinde alınan kararlar hakkında ne aşamada olduklarını her beş yılda bir göstermek zorunda. Buna göre ilk raporlama 2020'de olacak.

COP 21 Kararları Anlaşmayla birlikte sera gazı emisyonunu azaltacak ve sürdürülebilir kalkınmaya destek verecek bir mekanizma kurulması da kabul edildi. Anlaşmaya imza atan 195 ülke, emisyon kısıtlamalarını ölçmek ve gözlemlemek için bir yapı oluşturacak. Anlaşma, gelişmiş ülkelere gelişmekte olan ülkelerin kirliliği azaltmasında finansal destek sağlamasını zorunlu tutuyor.

İklim bilimciler ne düşünüyor? [Image 1] A survey conducted in 2007 by George Mason University of U.S. scientists who have expertise in climate science (not just a scientific background) what they think. 97% of the 489 respondents agreed that “global average temperatures have increased” during the past century. That’s up from 60% in 1991. [click, Image 2] 84% believe human activities are causing the warming, and only 5% disagree. So the survey does indicate the bulk of climate scientists—those most knowledgeable about the field—now agree that human activity contributes to global warming.