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Global_JJ Warming_NN1 has_VHZ for_IF many_DA2 years_NNT2 now_RT been_VBN an_AT1 issue_NN1 for_IF scientists_NN2 ._. 
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With_IW ,_, the_AT media_NN reporting_VVG headlines_NN2 such_II21 as_II22 "_" Rising_VVG concentrations_NN2 of_IO greenhouse_NN1 gases_NN2 may_VM have_VHI more_DAR serious_JJ impacts_NN2 than_CSN previously_RR believed_VVN "_" are_VBR we_PPIS2 right_RR to_TO believe_VVI what_DDQ they_PPHS2 are_VBR telling_VVG us_PPIO2 ?_? 
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In_II this_DD1 essay_NN1 what_DDQ evidence_NN1 is_VBZ available_JJ to_TO support_VVI this_DD1 statement_NN1 ,_, and_CC the_AT mechanisms_NN2 that_CST lead_VV0 to_II global_JJ warming_NN1 ._. 
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Around_RG 18000_MC years_NNT2 ago_RA ,_, the_AT earth_NN1 was_VBDZ in_II its_APPGE last_MD known_JJ "_" ice_NN1 age_NN1 "_" ._. 
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Glaciers_NN2 extended_VVD a_AT1 long_JJ way_NN1 south_ND1 from_II the_AT poles_NN2 well_RR into_II Europe_NP1 and_CC North_ND1 America_NP1 ._. 
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The_AT ice_NN1 was_VBDZ several_DA2 kilometres_NNU2 thick_JJ and_CC covered_VVD a_AT1 vast_JJ area_NN1 of_IO the_AT globe_NN1 ._. 
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In_II present_JJ times_NNT2 ,_, glaciers_NN2 only_RR account_VV0 for_IF 10%_NNU of_IO the_AT earth_NN1 's_GE surface_NN1 ._. 
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Geological_JJ surveys_NN2 have_VH0 found_VVN evidence_NN1 to_TO support_VVI the_AT changing_JJ earth_NN1 's_GE climate_NN1 ,_, showing_VVG the_AT process_NN1 is_VBZ both_RR slow_JJ and_CC continuous_JJ ._. 
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However_RR ,_, in_II recent_JJ time_NNT1 it_PPH1 has_VHZ been_VBN observed_VVN that_CST there_EX has_VHZ been_VBN a_AT1 marked_JJ increase_NN1 in_II temperature_NN1 at_II the_AT earth_NN1 's_GE surface_NN1 ._. 
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Figure_VV0 1_MC1 shows_VVZ estimates_NN2 of_IO the_AT average_JJ northern_JJ hemisphere_NN1 temperature_NN1 until_II 1850_MC after_II which_DDQ detailed_JJ observations_NN2 were_VBDR available_JJ to_TO produce_VVI the_AT data_NN ._. 
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It_PPH1 is_VBZ quite_RG clear_JJ on_II the_AT graph_NN1 that_CST although_CS there_EX have_VH0 been_VBN both_RR cooler_JJR and_CC warmer_JJR periods_NN2 leading_VVG up_II21 to_II22 about_II 1900_MC ,_, post_NN1 1900_MC there_EX is_VBZ a_AT1 marked_JJ consistent_JJ temperature_NN1 increase_NN1 unlike_II before_RT ._. 
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Experts_NN2 for_IF some_DD time_NNT1 have_VH0 been_VBN trying_VVG to_TO find_VVI some_DD patterns_NN2 in_II human_NN1 and_CC natural_JJ activities_NN2 that_CST might_VM have_VHI led_VVN to_II this_DD1 increase_NN1 in_II temperature_NN1 beyond_II what_DDQ they_PPHS2 would_VM see_VVI as_RG natural_JJ fluctuations_NN2 ._. 
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Greenhouse_NN1 gases_NN2 are_VBR those_DD2 which_DDQ scientists_NN2 believe_VV0 are_VBR the_AT main_JJ causes_NN2 of_IO global_JJ warming_NN1 ._. 
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Naturally_RR our_APPGE earths_NN2 atmosphere_NN1 reflects_VVZ some_DD incoming_JJ radiation_NN1 back_NN1 out_RP to_TO space_VVI whereas_CS other_JJ radiation_NN1 can_VM pass_VVI freely_RR through_RP into_II the_AT atmosphere_NN1 to_TO heat_VVI the_AT earth_NN1 ._. 
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As_II the_AT earths_NN2 surface_NN1 is_VBZ heated_VVN ,_, it_PPH1 radiates_VVZ the_AT heat_NN1 back_NN1 out_RP to_II the_AT atmosphere_NN1 ._. 
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In_II a_AT1 time_NNT1 when_RRQ there_EX were_VBDR few_DA2 greenhouses_NN2 gases_NN2 scientists_NN2 believe_VV0 more_DAR of_IO the_AT heat_NN1 was_VBDZ being_VBG radiated_VVN back_RP out_RP into_II space_NN1 ,_, whereas_CS now_RT the_AT greenhouse_NN1 gases_NN2 in_II the_AT atmosphere_NN1 are_VBR trapping_VVG some_DD of_IO the_AT outgoing_JJ heat_NN1 and_CC causing_VVG it_PPH1 to_TO be_VBI reflected_VVN back_RP to_II earth_NN1 ._. 
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The_AT effect_NN1 was_VBDZ initially_RR thought_VVN to_TO be_VBI similar_JJ to_II that_DD1 of_IO a_AT1 greenhouse_NN1 ;_; however_RR studies_NN2 proved_VVD it_PPH1 's_VBZ not_XX exactly_RR like_II a_AT1 greenhouse_NN1 !_! 
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The_AT main_JJ greenhouse_NN1 gases_NN2 in_II our_APPGE atmosphere_NN1 today_RT are_VBR water_NN1 vapour_NN1 ,_, carbon_NN1 dioxide_NN1 ,_, ozone_NN1 ,_, methane_NN1 ,_, nitrous_JJ oxide_NN1 and_CC CFC_NP1 's_GE ._. 
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Most_DAT of_IO the_AT greenhouse_NN1 gases_NN2 in_II the_AT atmosphere_NN1 today_RT have_VH0 existed_VVN here_RL naturally_RR for_IF many_DA2 years_NNT2 and_CC we_PPIS2 rely_VV0 on_II them_PPHO2 to_TO keep_VVI the_AT earth_NN1 at_II an_AT1 average_JJ temperature_NN1 of_IO 15C_FO ._. 
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If_CS the_AT gases_NN2 were_VBDR not_XX present_JJ then_RT the_AT earth_NN1 's_GE surface_NN1 temperature_NN1 would_VM be_VBI somewhere_RL is_VBZ the_AT region_NN1 of_IO -18C_FO ,_, which_DDQ would_VM be_VBI too_RG cold_JJ to_TO support_VVI a_AT1 lot_NN1 of_IO living_JJ creatures_NN2 on_II the_AT planet_NN1 ._. 
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It_PPH1 was_VBDZ not_XX until_CS the_AT western_JJ world_NN1 industrialised_JJ that_CST levels_NN2 of_IO greenhouses_NN2 gases_NN2 started_VVD to_TO rise_VVI rapidly_RR ._. 
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Carbon_NN1 dioxide_NN1 ,_, CO2_FO is_VBZ probably_RR the_AT most_RGT well_JJ known_JJ gas_NN1 that_CST is_VBZ associated_VVN with_IW the_AT global_JJ warming_NN1 ,_, produced_VVN as_II a_AT1 by_II product_NN1 of_IO the_AT burning_JJ of_IO fossil_NN1 fuels_NN2 such_II21 as_II22 wood_NN1 ,_, coal_NN1 and_CC oil_NN1 ._. 
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CO2_FO is_VBZ a_AT1 selective_JJ absorber_NN1 which_DDQ is_VBZ able_JK to_TO absorb_VVI strongly_RR outgoing_JJ infrared_JJ radiation_NN1 from_II the_AT earth_NN1 thereby_RR trapping_VVG the_AT energy_NN1 associated_VVN with_IW it_PPH1 in_II our_APPGE atmosphere_NN1 ._. 
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Pre_II industrialising_VVG the_AT amount_NN1 of_IO CO2_FO present_NN1 in_II the_AT atmosphere_NN1 was_VBDZ about_RG 280ppm_NNU and_CC today_RT levels_NN2 are_VBR about_RG 375ppm_NNU ._. 
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In_II the_AT last_MD 25_MC years_NNT2 CO2_FO levels_NN2 have_VH0 risen_VVN around_RG 10%_NNU and_CC this_DD1 looks_VVZ set_NN1 to_TO continue_VVI with_IW more_DAR of_IO the_AT world_NN1 industrialising_VVG ._. 
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<s>
Other_JJ greenhouse_NN1 gases_NN2 such_II21 as_II22 methane_NN1 and_CC nitrous_JJ oxide_NN1 have_VH0 also_RR increase_VV0 in_II concentration_NN1 over_II the_AT past_JJ few_DA2 years_NNT2 ._. 
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Both_DB2 of_IO these_DD2 gases_NN2 are_VBR also_RR good_JJ absorbers_NN2 of_IO infrared_JJ radiation_NN1 and_CC add_VV0 to_II the_AT overall_JJ warming_NN1 of_IO the_AT earth_NN1 ._. 
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Methane_NN1 is_VBZ given_VVN off_RP by_II coal_NN1 ,_, natural_JJ gas_NN1 and_CC oil_NN1 however_RR more_RGR naturally_RR it_PPH1 is_VBZ produced_VVN by_II the_AT decomposition_NN1 of_IO organic_JJ waste_NN1 and_CC by_II livestock_NN ._. 
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Methane_NN1 is_VBZ far_RG more_RGR effective_JJ at_II trapping_VVG heat_NN1 than_CSN CO2_FO ._. 
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Its_APPGE level_NN1 although_CS have_VH0 risen_VVN in_II recent_JJ years_NNT2 have_VH0 tended_VVN to_TO stabilise_VVI at_II around_II 1750ppb_FO ._. 
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Nitrous_JJ Oxide_NN1 is_VBZ given_VVN off_RP by_II both_DB2 industrial_JJ and_CC natural_JJ processes_NN2 ._. 
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There_EX has_VHZ been_VBN a_AT1 steady_JJ rise_NN1 of_IO NO_AT 2_MC over_II recent_JJ years_NNT2 also_RR and_CC this_DD1 too_RR is_VBZ adding_VVG to_II the_AT greenhouse_NN1 effect_NN1 ._. 
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Perhaps_RR more_RGR worryingly_RR is_VBZ the_AT effects_NN2 caused_VVN by_II pollutants_NN2 created_VVN by_II man_NN1 in_II recent_JJ years_NNT2 which_DDQ are_VBR not_XX natural_JJ greenhouse_NN1 gases_NN2 ._. 
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<s>
CFC_NP1 's_GE were_VBDR first_MD created_VVN during_II World_NN1 War_NN1 Two_MC as_CSA propellants_NN2 ._. 
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<s>
These_DD2 gases_NN2 were_VBDR so_RG useful_JJ that_CST after_CS the_AT war_NN1 they_PPHS2 became_VVD propellants_NN2 for_IF whole_JJ host_NN1 of_IO products_NN2 including_II domestic_JJ products_NN2 such_II21 as_II22 deodorants_NN2 ._. 
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<s>
The_AT use_NN1 of_IO CFC_NP1 's_GE has_VHZ all_RR21 but_RR22 been_VBN phased_VVN out_RP worldwide_RL now_RT ,_, and_CC production_NN1 at_RR21 least_RR22 in_II the_AT European_JJ Union_NN1 finished_VVD around_RG 1996_MC ._. 
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CFC_NP1 's_VHZ had_VHN a_AT1 destructive_JJ effect_NN1 on_II the_AT ozone_NN1 layer_NN1 ._. 
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<s>
In_II 1991_MC scientists_NN2 worldwide_RL conducted_VVD a_AT1 survey_NN1 on_II the_AT ozone_NN1 layer_NN1 and_CC found_VVD that_CST since_CS about_RG 1979_MC to_II 1991_MC the_AT ozone_NN1 levels_NN2 reduced_VVN by_II 5-6%_FO ._. 
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<s>
Although_CS this_DD1 may_VM not_XX sound_VVI like_II a_AT1 very_RG large_JJ amount_NN1 ,_, it_PPH1 has_VHZ caused_VVN a_AT1 12%_NNU increase_NN1 in_II UV_JJ levels_NN2 in_II New_NP1 Zealand_NP1 between_II 1990_MC and_CC 1999_MC ._. 
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<s>
Apart_II21 from_II22 the_AT human_JJ factors_NN2 which_DDQ have_VH0 added_VVN to_II the_AT natural_JJ greenhouse_NN1 gases_NN2 there_EX are_VBR a_AT1 further_JJR number_NN1 of_IO reasons_NN2 as_II21 to_II22 why_RRQ global_JJ warming_NN1 could_VM be_VBI occurring_VVG ._. 
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<s>
Plates_NN2 with_IW glacial_JJ features_NN2 can_VM be_VBI found_VVN near_II sea_NN1 level_NN1 in_II Africa_NP1 which_DDQ suggests_VVZ a_AT1 large_JJ shifting_NN1 of_IO the_AT plates_NN2 over_II a_AT1 period_NN1 of_IO time_NNT1 ._. 
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It_PPH1 is_VBZ highly_RR unlikely_JJ that_CST any_DD glaciers_NN2 ever_RR extended_VVN this_RG far_RR from_II the_AT poles_NN2 and_CC there_EX is_VBZ little_DA1 evidence_NN1 to_TO support_VVI it_PPH1 ._. 
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Shifting_JJ tectonic_JJ plates_NN2 also_RR cause_VV0 volcanoes_NN2 to_TO form_VVI along_II21 with_II22 underwater_JJ ridges_NN2 ._. 
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<s>
The_AT speed_NN1 at_II which_DDQ plates_NN2 move_VV0 could_VM have_VHI an_AT1 effect_NN1 on_II our_APPGE climate_NN1 ,_, for_REX21 instance_REX22 when_CS the_AT plates_NN2 are_VBR moving_VVG rapidly_RR there_EX is_VBZ likely_JJ to_TO be_VBI an_AT1 increase_NN1 in_II the_AT rate_NN1 at_II which_DDQ volcanoes_NN2 both_RR form_VV0 and_CC erupt_NN1 ._. 
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<s>
Erupting_VVG volcanoes_NN2 produces_VVZ greenhouse_NN1 gases_NN2 such_II21 as_II22 CO2_FO ,_, H_ZZ1 2O_FO ,_, SO_RG 2_MC and_CC N_ZZ1 2_MC which_DDQ add_VV0 to_II global_JJ warming_NN1 ._. 
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<s>
A_AT1 secondary_JJ effect_NN1 is_VBZ that_CST ashes_NN2 from_II the_AT eruption_NN1 which_DDQ vaporises_VVZ in_II the_AT upper_JJ atmosphere_NN1 forming_VVG a_AT1 small_JJ dense_JJ layer_NN1 of_IO haze_NN1 that_CST absorbs_VVZ and_CC reflects_VVZ back_RP for_IF many_DA2 years_NNT2 an_AT1 amount_NN1 of_IO incoming_JJ radiation_NN1 from_II the_AT earth_NN1 ._. 
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<s>
After_CS the_AT 1991_MC eruption_NN1 of_IO Mount_NNL1 Pinatubo_NP1 scientists_NN2 predicted_VVD a_AT1 0.5C_FO fall_VV0 in_II global_JJ temperatures_NN2 and_CC in_II the_AT following_JJ three_MC years_NNT2 this_DD1 happened_VVD ._. 
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<s>
Underwater_JJ ridges_NN2 can_VM have_VHI an_AT1 effect_NN1 also_RR ,_, they_PPHS2 can_VM displace_VVI large_JJ amounts_NN2 of_IO sea_NN1 water_NN1 thus_RR causing_VVG sea_NN1 level_NN1 rising_VVG ,_, along_II21 with_II22 releasing_VVG a_AT1 whole_JJ host_NN1 of_IO greenhouse_NN1 gases_NN2 ._. 
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<s>
The_AT oceans_NN2 themselves_PPX2 are_VBR absorbers_NN2 of_IO CO2_FO and_CC have_VH0 a_AT1 large_JJ part_NN1 to_TO play_VVI in_II stopping_VVG global_JJ warming_NN1 getting_VVG out_II21 of_II22 control_NN1 ._. 
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<s>
Recent_JJ studies_NN2 ,_, as_RG late_RR as_CSA 2005_MC in_II Germany_NP1 have_VH0 shown_VVN that_DD1 biomass_NN1 carbon_NN1 in_II the_AT oceans_NN2 represents_VVZ a_AT1 way_NN1 of_IO long_JJ term_NN1 storage_NN1 ._. 
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<s>
It_PPH1 was_VBDZ shown_VVN some_DD years_NNT2 earlier_RRR that_DD1 adding_VVG small_JJ iron_NN1 or_CC sulphate_NN1 particles_NN2 to_II the_AT ocean_NN1 can_VM stimulate_VVI the_AT growth_NN1 of_IO plankton_NN1 ,_, whereas_CS the_AT natural_JJ oceans_NN2 supply_NN1 of_IO this_DD1 has_VHZ been_VBN decreasing_VVG over_RP recent_JJ times_NNT2 ._. 
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The_AT increased_JJ productivity_NN1 of_IO the_AT oceans_NN2 through_II this_DD1 may_VM have_VHI a_AT1 positive_JJ effect_NN1 on_II reducing_VVG global_JJ warming_NN1 ,_, as_CSA it_PPH1 can_VM be_VBI shown_VVN that_CST between_II 10,000_MC and_CC 100,000_MC carbon_NN1 atoms_NN2 can_VM be_VBI "_" sunk_VVN "_" for_IF each_DD1 iron_NN1 atom_NN1 added_VVN to_II the_AT ocean_NN1 ._. 
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However_RRQV the_AT method_NN1 should_VM be_VBI used_VVN with_IW care_NN1 ,_, as_CSA increased_JJ carbon_NN1 levels_NN2 in_II the_AT ocean_NN1 lead_NN1 to_II it_PPH1 becoming_VVG increasingly_RR acidic_JJ ._. 
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<s>
A_AT1 rise_NN1 in_II sea_NN1 level_NN1 would_VM mean_VVI that_CST more_DAR land_NN1 is_VBZ covered_VVN ,_, and_CC vegetation_NN1 which_DDQ is_VBZ important_JJ for_IF the_AT removal_NN1 of_IO CO2_FO from_II the_AT atmosphere_NN1 ._. 
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A_AT1 rise_NN1 in_II sea_NN1 level_NN1 could_VM be_VBI caused_VVN by_II water_NN1 being_VBG displaced_VVN by_II underwater_JJ ridges_NN2 ,_, the_AT melting_NN1 of_IO glaciers_NN2 from_II the_AT increased_JJ temperature_NN1 or_CC also_RR from_II the_AT increased_JJ energy_NN1 in_II the_AT atmosphere_NN1 causing_VVG the_AT oceans_NN2 to_TO expand_VVI ._. 
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<s>
Naturally_RR large_JJ parts_NN2 of_IO the_AT earth_NN1 are_VBR rich_JJ in_II vegetation_NN1 which_DDQ converts_VVZ CO2_FO to_II O_ZZ1 2_MC ;_; however_RR deforestation_NN1 is_VBZ happening_VVG on_II a_AT1 large_JJ scale_NN1 worldwide_RL everyday_JJ which_DDQ means_VVZ that_CST even_CS21 though_CS22 we_PPIS2 have_VH0 an_AT1 increasing_JJ amount_NN1 of_IO CO2_FO being_VBG released_VVN into_II the_AT atmosphere_NN1 the_AT amount_NN1 of_IO vegetation_NN1 available_JJ to_TO convert_VVI it_PPH1 back_RP to_II O_ZZ1 2_MC is_VBZ being_VBG reduced_VVN ._. 
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<s>
At_II current_JJ rates_NN2 ,_, if_CS deforestation_NN1 continued_VVD then_RT the_AT "_" world_NN1 's_GE rain_NN1 forests_NN2 will_VM vanish_VVI within_II 100_MC years_NNT2 "_" 2_MC ._. 
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<s>
Soil_NN1 is_VBZ a_AT1 good_JJ storage_NN1 for_IF carbon_NN1 ,_, about_RG twice_RR as_RG good_JJ as_CSA storage_NN1 above_II ground_NN1 ._. 
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Carbon_NN1 levels_NN2 in_II the_AT ground_NN1 have_VH0 lowered_VVN over_II recent_JJ years_NNT2 are_VBR more_RRR has_VHZ been_VBN released_VVN to_II above_JJ ground_NN1 storage_NN1 ._. 
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In_II grassy_JJ areas_NN2 and_CC unploughed_JJ fields_NN2 the_AT storage_NN1 of_IO carbon_NN1 means_VVZ it_PPH1 can_VM remain_VVI un-oxidised_JJ for_IF many_DA2 years_NNT2 however_RR with_IW fields_NN2 being_VBG dug_VVN for_IF development_NN1 and_CC agricultural_JJ systems_NN2 being_VBG put_VVN in_II place_NN1 much_DA1 of_IO the_AT carbon_NN1 has_VHZ been_VBN released_VVN ._. 
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When_CS it_PPH1 becomes_VVZ oxidised_JJ as_CSA CO2_FO it_PPH1 becomes_VVZ a_AT1 greenhouse_NN1 gas_NN1 adding_VVG to_II the_AT global_JJ warming_NN1 effect_NN1 ._. 
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The_AT changing_NN1 of_IO the_AT earths_NN2 orbit_NN1 is_VBZ also_RR believed_VVN to_TO have_VHI some_DD effect_NN1 on_II global_JJ temperatures_NN2 ._. 
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The_AT effect_NN1 ,_, known_VVN as_II Milankovitch_NP1 theory_NN1 can_VM be_VBI summed_VVN up_RP as_CSA that_DD1 as_II the_AT earth_NN1 moves_VVZ through_II space_NN1 ,_, "_" three_MC separate_JJ cyclic_JJ movements_NN2 combine_VV0 to_TO produce_VVI variations_NN2 in_II the_AT amount_NN1 of_IO solar_JJ energy_NN1 that_CST falls_VVZ on_II the_AT earth_NN1 "_" 3_MC ._. 
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At_RR21 present_RR22 we_PPIS2 are_VBR in_II a_AT1 period_NN1 that_CST the_AT closest_JJT time_NNT1 to_II the_AT sun_NN1 is_VBZ January_NPM1 ,_, and_CC this_DD1 alters_VVZ around_RP every_AT1 100,000_MC years_NNT2 ._. 
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This_DD1 ties_VVZ in_RP well_RR with_IW evidence_NN1 found_VVD that_CST suggests_VVZ that_DD1 ice_NN1 sheets_NN2 peak_VV0 around_RP every_AT1 100,000_MC years_NNT2 or_CC so_RR ._. 
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Smaller_JJR peaks_NN2 were_VBDR noticed_VVN at_II around_RG 23,000_MC and_CC 11,000_MC years_NNT2 which_DDQ are_VBR also_RR significant_JJ in_II the_AT Milankovitch_NN1 theory_NN1 ,_, however_RRQV levels_NN2 of_IO CO2_FO at_II this_DD1 time_NNT1 are_VBR considerably_RR lower_JJR than_CSN today_RT and_CC therefore_RR the_AT CO2_FO can_VM not_XX be_VBI the_AT single_JJ reason_NN1 for_IF climate_NN1 change_NN1 ._. 
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Variation_NN1 in_II the_AT solar_JJ output_NN1 can_VM also_RR have_VHI an_AT1 effect_NN1 on_II our_APPGE climate_NN1 ._. 
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<s>
The_AT sun_NN1 's_GE output_NN1 has_VHZ been_VBN linked_VVN by_II astronomers_NN2 to_II sun_NN1 spots_NN2 ,_, which_DDQ peak_VV0 cyclically_RR every_AT1 11_MC years_NNT2 ._. 
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Although_CS it_PPH1 may_VM sound_VVI small_JJ ,_, there_EX is_VBZ a_AT1 0.1%_FO different_JJ between_II periods_NN2 of_IO maximum_NN1 and_CC minimum_JJ output_NN1 ._. 
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Ozone_NN1 levels_NN2 increase_VV0 at_II the_AT peaks_NN2 ,_, absorbing_VVG the_AT extra_JJ UV_JJ radiation_NN1 but_CCB this_DD1 has_VHZ a_AT1 further_JJR effect_NN1 of_IO warming_VVG the_AT stratosphere_NN1 and_CC thus_RR creating_VVG temperature_NN1 gradients_NN2 in_II troposphere_NN1 ,_, which_DDQ seem_VV0 to_TO have_VHI a_AT1 circulatory_JJ effect_NN1 on_II the_AT Hadley_NP1 cell_NN1 for_REX21 instance_REX22 ._. 
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There_EX is_VBZ little_RR firm_JJ evidence_NN1 to_TO support_VVI the_AT fluctuation_NN1 in_II solar_JJ output_NN1 with_IW climate_NN1 change_NN1 because_CS there_EX is_VBZ simply_RR not_XX enough_DD data_NN available_JJ at_RR21 present_RR22 and_CC it_PPH1 unlikely_JJ there_EX will_VM such_DA data_NN available_JJ for_IF many_DA2 years_NNT2 to_TO come_VVI ._. 
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From_II the_AT small_JJ area_NN1 I_PPIS1 have_VH0 been_VBN able_JK to_TO cover_VVI about_II this_DD1 vast_JJ subject_NN1 ,_, it_PPH1 is_VBZ obvious_JJ to_TO see_VVI that_CST the_AT earth_NN1 is_VBZ undergoing_VVG a_AT1 constant_JJ climate_NN1 change_NN1 ._. 
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The_AT earth_NN1 was_VBDZ once_RR been_VBN much_RR warmer_JJR and_CC similarly_RR once_RR much_RR colder_JJR than_CSN it_PPH1 is_VBZ today_RT ._. 
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During_II the_AT last_MD 200_MC years_NNT2 the_AT earth_NN1 surface_NN1 temperature_NN1 has_VHZ steadily_RR risen_VVN and_CC there_EX is_VBZ firm_JJ evidence_NN1 unlike_II before_RT of_IO this_DD1 ._. 
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Actual_JJ recording_NN1 of_IO the_AT climate_NN1 rather_II21 than_II22 geological_JJ studies_NN2 can_VM give_VVI us_PPIO2 much_RR more_DAR confidence_NN1 of_IO the_AT change_NN1 we_PPIS2 are_VBR undergoing_VVG ,_, and_CC in_II a_AT1 developed_JJ world_NN1 it_PPH1 is_VBZ something_PN1 to_TO be_VBI concerned_JJ about_II ._. 
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