Sera gazları –karbon dioksit (CO 2 ), su buharı, metan ve diğerleri– Dünya'ya gelen ve tekrar uzaya yansıyan ısıyı tutarak yeryüzünü ısıtıyor. Sanayi devrimi öncesindeki binlerce yıl boyunca atmosferdeki sera gazları görece kararlı bir düzeyde kalırken, o dönemden beri fosil yakıt tüketimi gibi insan faaliyetleri bu düzeyin yükselmesine neden oldu. Sera gazı oranlarının artması ısınmayı yoğunlaştırıyor.
BM Hükümetlerarası İklim Değişikliği Paneli'nin 2001 raporuna göre “son 50 yılda gözlemlenen ısınmanın sera gazı oranlarının artışından kaynaklandığı söylenebilir”. ABD, en önemli sera gazlarından biri olan karbon dioksiti dünyada en fazla açığa çıkaran ülke. Oak Ridge Ulusal Laboratuvarı'nın 2000'de fosil yakıt tüketimi, çimento üretimi ve gaz yanmasının neden olduğu toplam CO 2 salınımı açısından yaptığı sıralamayı aşağıdaki listede görebilirsiniz. 1 ANTARCTIC FISHERIES 61.12 2 U.S. VIRGIN ISLANDS 29.91 3 QATAR 19.65 4 NETHERLAND ANTILLES 12.61 5 BAHRAIN 7.70 6 GUAM 7.17 7 UNITED ARAB EMIRATES 6.17 8 KUWAIT 5.97 9 TRINIDAD AND TOBAGO 5.58 10 UNITED STATES OF AMERICA 5.40 11 LUXEMBOURG 5.31 12 FALKLAND ISLANDS (MALVINAS) 5.24 13 ARUBA 5.20 14 BRUNEI (DARUSSALAM) 5.08 15 WAKE ISLAND 5.02 16 AUSTRALIA 4.91 17 SAUDI ARABIA 4.77 18 SINGAPORE 3.90 19 CANADA 3.87 20 FAEROE ISLANDS 3.84 21 PALAU 3.48 22 ESTONIA 3.19 23 CZECH REPUBLIC 3.16 24 NAURU 3.07 25 IRELAND 3.04 26 NORWAY 3.03 27 LIBYAN ARAB JAMAHIRIYAH 2.95 28 ISRAEL 2.85 29 FINLAND 2.82 30 BELGIUM 2.72 31 GREENLAND 2.71 32 RUSSIAN FEDERATION 2.69 33 TAIWAN 2.68 34 MONTSERRAT 2.68 35 GERMANY 2.61 36 UNITED KINGDOM 2.59 37 JAPAN 2.55 38 REPUBLIC OF KOREA 2.47 39 GREECE 2.44 40 NETHERLANDS 2.39 41 CYPRUS 2.32 42 DEMOCRATIC PEOPLE'S REPUBLIC OF KOREA 2.31 43 NEW ZEALAND 2.28 44 DENMARK 2.28 45 OMAN 2.25 46 KAZAKHSTAN 2.22 47 GIBRALTAR 2.20 48 NEW CALEDONIA 2.16 49 ST. PIERRE & MIQUELON 2.15 50 POLAND 2.13 51 ICELAND 2.10 52 CAYMAN ISLANDS 2.05 53 AUSTRIA 2.05 54 SOUTH AFRICA 2.04 55 ITALY (INCLUDING SAN MARINO) 2.02 56 BERMUDA 2.01 57 SLOVENIA 2.01 58 TURKMENISTAN 1.99 59 MALTA 1.96 60 SPAIN 1.95 61 UKRAINE 1.89 62 SLOVAKIA 1.79 63 VENEZUELA 1.78 64 MALAYSIA 1.69 65 FRANCE (INCLUDING MONACO) 1.68 66 PORTUGAL 1.63 67 BAHAMAS 1.62 68 BELARUS 1.61 69 FRENCH GUIANA 1.52 70 MACEDONIA 1.50 71 ANTIGUA & BARBUDA 1.48 72 MARTINIQUE 1.47 73 HUNGARY 1.47 74 SWITZERLAND 1.46 75 BULGARIA 1.45 76 SWEDEN 1.44 77 ISLAMIC REPUBLIC OF IRAN 1.33 78 HONG KONG 1.33 79 SURINAME 1.33 80 BOSNIA-HERZEGOVINIA 1.32 81 UZBEKISTAN 1.31 82 CROATIA 1.22 83 BARBADOS 1.20 84 MEXICO 1.19 85 LEBANON 1.18 86 AMERICAN SAMOA 1.15 87 JAMAICA 1.12 88 FEDERAL REPUBLIC OF YUGOSLAVIA 1.07 89 CHILE 1.07 90 ROMANIA 1.05 91 GUADELOUPE 1.05 92 MACAU 1.02 93 ARGENTINA 1.02 94 AZERBAIJAN 0.99 95 TURKEY 0.93 96 REUNION 0.92 97 IRAQ 0.91 98 SYRIAN ARAB REPUBLIC 0.91 99 LITHUANIA 0.88 100 THAILAND 0.87 101 JORDAN 0.86 102 MONGOLIA 0.86 103 BELIZE 0.85 104 DOMINICAN REPUBLIC 0.81 105 ALGERIA 0.80 106 GABON 0.79 107 SEYCHELLES 0.76 108 CUBA 0.75 109 ST. KITTS-NEVIS 0.69 110 LATVIA 0.67 111 SAINT HELENA 0.67 112 MAURITIUS 0.67 113 BRITISH VIRGIN ISLANDS 0.66 114 FRENCH POLYNESIA 0.64 115 BOTSWANA 0.64 116 SAINT LUCIA 0.62 117 PUERTO RICO 0.61 118 EGYPT 0.61 119 PANAMA 0.61 120 CHINA (MAINLAND) 0.60 121 GRENADA 0.57 122 GUYANA 0.57 123 ECUADOR 0.55 124 TUNISIA 0.53 125 MALDIVES 0.50 126 BRAZIL 0.50 127 REPUBLIC OF MOLDOVA 0.49 128 URUGUAY 0.44 129 COOK ISLANDS 0.42 130 NIUE 0.42 131 ST. VINCENT & THE GRENADINES 0.41 132 COSTA RICA 0.39 133 DOMINICA 0.38 134 COLOMBIA 0.38 135 BOLIVIA 0.36 136 INDONESIA 0.35 137 MOROCCO 0.35 138 TONGA 0.33 139 GEORGIA 0.32 140 ZIMBABWE 0.32 141 MAURITANIA 0.31 142 PERU 0.31 143 INDIA 0.29 144 EL SALVADOR 0.29 145 PHILIPPINES 0.28 146 NAMIBIA 0.27 147 WESTERN SAHARA 0.26 148 KYRGYZSTAN 0.26 149 ARMENIA 0.25 150 ALBANIA 0.25 151 FIJI 0.24 152 GUATEMALA 0.24 153 SAMOA 0.22 154 PAKISTAN 0.21 155 HONDURAS 0.20 156 VIET NAM 0.20 157 NICARAGUA 0.20 158 PARAGUAY 0.18 159 SAO TOME & PRINCIPE 0.18 160 TAJIKISTAN 0.18 161 COTE D IVOIRE 0.17 162 DJIBOUTI 0.17 163 CONGO 0.16 164 SRI LANKA 0.14 165 PAPUA NEW GUINEA 0.14 166 ANGOLA 0.13 167 YEMEN 0.13 168 EQUATORIAL GUINEA 0.12 169 REPUBLIC OF CAMEROON 0.12 170 SENEGAL 0.12 171 SWAZILAND 0.11 172 VANUATU 0.11 173 TOGO 0.11 174 SOLOMON ISLANDS 0.10 175 CAPE VERDE 0.09 176 GHANA 0.09 177 NIGERIA 0.09 178 KENYA 0.08 179 KIRIBATI 0.08 180 BENIN 0.07 181 GUINEA BISSAU 0.06 182 BANGLADESH 0.06 183 GAMBIA 0.05 184 MYANMAR 0.05 185 BHUTAN 0.05 186 HAITI 0.05 187 ZAMBIA 0.05 188 SUDAN 0.05 189 ERITREA 0.05 190 GUINEA 0.04 191 NEPAL 0.04 192 MADAGASCAR 0.04 193 LIBERIA 0.04 194 SIERRA LEONE 0.04 195 UNITED REPUBLIC OF TANZANIA 0.03 196 COMOROS 0.03 197 NIGER 0.03 198 BURKINA FASO 0.02 199 LAO PEOPLE'S DEMOCRATIC REPUBLIC 0.02 200 RWANDA 0.02 201 CENTRAL AFRICAN REPUBLIC 0.02 202 UGANDA 0.02 203 MALAWI 0.02 204 MOZAMBIQUE 0.02 205 ZAIRE 0.01 206 MALI 0.01 207 AFGHANISTAN 0.01 208 CAMBODIA 0.01 209 BURUNDI 0.01 210 CHAD 0.00 211 TURKS AND CAICOS ISLANDS 0.00 212 ETHIOPIA