【正文】 has H IV and you use the sam e needl e, you coul d i nject the virus i nto your own bl ood. do not share anythi ng el se that a person has used whil e i njecting drugs. Bl od coul d have spil t on i t. If you have sex wi th a m ale or a fem al e: use a condom. Thi s wi l prevent sexual flui d passi ng from one person to another. The fol l owi ng statem ents are NOT true. A person cannot get H IV the first tim e they have sex. WRON G. If one sexual partner has H IV, the other partner coul d bee i nfected. You can tel l by l ooki ng at someone whether or not they have H IV. WRON G. Many peopl e caryi ng H IV l ook perfectl y heal thy. It i s onl y when the di sease has progressed to AIDS that a person begi ns to l ook si ck. O nl y hom osexual s get AIDS. WRO N G. Anyone who has sex wi th a person infected wi th H IV/AIDS ri sks getti ng the vi rus. Wom en are sli ghtl y m ore l i kel y to be e i nfected than m en. If you hug, touch or kiss som eone wi th AIDS or vi si t them i n thei r hom e, you wil l get H IV/AIDS. WRON G. You can onl y get the di sease from bl ood or sexual fl ui d. Unfortunatel y, peopl e wi th HIV som etim es l ose thei r fri ends because of prejudi ce. Many peopl e are afrai d that they wi l get H IV/AIDS from those i nfected wi th H IV/AIDS. For the sam e reason, som e AIDS pati ents cannot fi nd anyone to l ook after them when they are si ck. You can get H IV/AIDS from m osqui toes. WRON G. There i s no evi dence of thi s. Unit 4 TH E EARTH IS BECOMIN G WARMER BUT DO ES IT MATTER? Duri ng the 20th century the tem perature of the earth rose about one degree Fahrenhei t. That probabl y does not seem m uch to you or m e, but it i s a rapi d i ncrease when pared to other natural changes. So how has thi s e about and does i t m ater? Earth Care?s Sophi e Armstrong expl ores these questi ons. There i s no doubt that the earth i s bei ng warm er (see Graph 1) and that i s i t hum an activi ty that has caused thi s gl obal warm i ng rather than a random but natural phenom enon. Al l sci enti sts subscri be to the vi ew that the i ncrease i n the earth?s tem perature i s due to the burni ng of fossi l fuel s l i ke coal, natural gas and oi l to produce energy. Some byproducts of thi s process are cal l ed “greenhouse” gases, the m ost im portant one of whi ch i s carbon dioxi de. Dr Jani ce Foster explai ns: “There i s a natural phenom enon that sci enti sts cal l the ?greenhouse effect?. Thi s is when sm al am ounts of gases i n the atm osphere, li ke carbon dioxi de, m ethane and water vapor, trap heat from the sun and therefore warm the earth. Wi thout the ?greenhouse effect?, the earth woul d be about thi rtythree degrees Cel si us cool er than i t is. So, we need those gases. The probl em begi ns when we add huge quanti ti es of extra carbon di oxi de i nto the atm osphere. It m eans that m ore heat energy tends to be trapped i n the atm osphere causi ng the global tem perature to go up. ” We know that the l evel s of carbon di oxi de have i ncreased greatl y over the last 100 to 150 years. It was a sci enti st cal ed Charl es Keeli ng, who m ade accurate m easurem ents of the amount of carbon di oxi de i n the atmosphere from 1957 to 1997. H e found that between these years the carbon di oxi de i n the atm osphere went up from around 315 parts to around 370 parts per m il li on (see Graph 2). Al l scientists accept thi s data. They also agree that i t i s the burni ng of m ore and more fossi l fuel s that has resulted i n thi s increase in carbon di oxi de. So how hi gh wil l the tem perature i ncrease go? Dr Jani ce Foster says that over the next 100 years the am ount of warmi ng coul d be as l ow as 1 to 1. 5 degrees Cel si us, but i t coul d be as hi gh as 5 degres. H owever, the ati tudes of sci enti sts towards thi s rise are pl etel y di fferent. O n the one hand, Dr Foster thi nks that the trend whi ch i ncreases the tem perature by 5 degrees woul d be a catastrophe. She says, “We can?t predi ct the cl im ate wel enough to know what to expect, but i t coul d be very seri ous. ” Others who agree wi th her thi nk there m ay be a rise of several m etres i n the sea l evel, or predi ct severe storm s, fl oods, droughts, fami nes, the spread of di seases and the di sappearance of speci es. On the other hand, there are those, l i ke Gee H am bl ey, who are opposed to thi s vi ew and beli eve that we shoul d not worry about hi gh l evel s of carbon di oxi de i n the ai r. They predi ct that any warm i ng wil l be mi l d with few bad environmental consequences. In fact, H am bl ey states, ” More carbon di oxi de i s actual l y a positi ve thi ng. It wil l m ake pl ants grow qui cker。 ARE YOU AT RISK? H IV i s a vi rus. A virus i s a very smal l i vi ng thing that causes di sease. There are many di fferent vi ruses, for exam pl e, the fl u vi rus or the SARS vi rus. H IV weakens a person?s imm une system。 i n fa。 crops wil l produce m ore。 i t wi l encourage a greater range of anim al s – al l of whi ch wil l make l ife for hum an beings better. ” Greenhouse gases continue to bui l d up i n the atm osphere. Even i f we start reduci ng the am ount of carbon di oxi de and other greenhouse gases, the cli mate i s going to keep on warmi ng for decades or centuries. No one knows the effects of global warming. Does that mean we should do nothi ng? Or, are the ri sks too great? WHAT CAN WE DO ABOUT GLOBAL WARMING? Dear Earth Care, I am doi ng a project on behalf of my school about gl obal warm ing. Sometimes I feel that indivi dual s can have l ittle effect on such huge envi ronm ental probl ems. However, I stil thi nk peopl e should advocate i mprovem ents i n the way we use energy today. As I?m not sure where to start with my project, I woul d appreci ate any suggesti ons you may have. Thank you Ouyang Guang Dear Ouyang Guang, There are many peopl e